Backport #10723: Remove unused -XCPP

[mergify]

Fixes #10720, a follow on from #10092. Removes unused {-# LANGUAGE CPP #-} pragmas.

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Template B: This PR does not modify behaviour or interface

• Patches conform to the coding conventions.
• Is this a PR that fixes CI? If so, it will need to be backported to older cabal release branches (ask maintainers for directions).

Manual QA Notes

Please delete dist-newstyle and run the following to check for occurrences of unused -XCPP:

$ grep '^#if' --files-without-match $(grep -R --files-with-matches 'LANGUAGE.*CPP' */**/*.hs)
cabal-testsuite/PackageTests/Backpack/bkpcabal01/p/P.hs
cabal-testsuite/PackageTests/CabalMacros/Mdl.hs
cabal-testsuite/PackageTests/CmmSources/src/Demo.hs
cabal-testsuite/PackageTests/CmmSourcesDyn/demo/Main.hs
cabal-testsuite/PackageTests/CmmSourcesDyn/src/Demo.hs
cabal-testsuite/PackageTests/CmmSourcesExe/src/Demo.hs
cabal-testsuite/PackageTests/Haddock/CPP.hs
cabal-testsuite/PackageTests/PreProcess/Hsc2HsOptionsCC/Main.hs
cabal-testsuite/PackageTests/Regression/T5386/Foo.hs
Cabal/src/Distribution/Simple/Build/PathsModule/Z.hs

$ grep 'LANGUAGE CPP' Cabal/src/Distribution/Simple/Build/PathsModule/Z.hs
    tell "{-# LANGUAGE CPP #-}\n"

Those in cabal-testsuite/PackageTests are part of tests so should likely stay put and Distribution.Simple.Build.PathsModule.Z is generating a paths module using a zinza template. It's a false positive find with the unrefined grep pattern, LANGUAGE.*CPP.

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This is an automatic backport of pull request #10723 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 7965c7f has failed:

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Changes to be committed:
	modified:   Cabal-QuickCheck/src/Test/QuickCheck/GenericArbitrary.hs
	modified:   Cabal-syntax/src/Distribution/Compat/Exception.hs
	modified:   Cabal-syntax/src/Distribution/Compat/Graph.hs
	modified:   Cabal-syntax/src/Distribution/Compat/MonadFail.hs
	modified:   Cabal-syntax/src/Distribution/Compat/Newtype.hs
	modified:   Cabal-syntax/src/Distribution/Compat/Prelude.hs
	modified:   Cabal-syntax/src/Distribution/Compat/Semigroup.hs
	modified:   Cabal-syntax/src/Distribution/FieldGrammar/Class.hs
	modified:   Cabal-syntax/src/Distribution/Fields/ParseResult.hs
	modified:   Cabal-syntax/src/Distribution/PackageDescription/Parsec.hs
	modified:   Cabal-syntax/src/Distribution/Parsec.hs
	modified:   Cabal-syntax/src/Distribution/System.hs
	modified:   Cabal-tests/tests/UnitTests/Distribution/CabalSpecVersion.hs
	modified:   Cabal-tests/tests/UnitTests/Distribution/Utils/CharSet.hs
	modified:   Cabal-tests/tests/UnitTests/Distribution/Utils/Structured.hs
	modified:   Cabal-tree-diff/src/Data/TreeDiff/Instances/Cabal.hs
	modified:   Cabal-tree-diff/src/Data/TreeDiff/Instances/CabalLanguage.hs
	modified:   Cabal-tree-diff/src/Data/TreeDiff/Instances/CabalSPDX.hs
	modified:   Cabal-tree-diff/src/Data/TreeDiff/Instances/CabalVersion.hs
	modified:   Cabal/src/Distribution/Compat/Async.hs
	modified:   Cabal/src/Distribution/Compat/ResponseFile.hs
	modified:   Cabal/src/Distribution/Compat/Stack.hs
	modified:   Cabal/src/Distribution/Simple/GHCJS.hs
	modified:   Cabal/src/Distribution/Simple/Setup.hs
	modified:   Cabal/src/Distribution/Simple/Setup/Benchmark.hs
	modified:   Cabal/src/Distribution/Simple/Setup/Build.hs
	modified:   Cabal/src/Distribution/Simple/Setup/Clean.hs
	modified:   Cabal/src/Distribution/Simple/Setup/Common.hs
	modified:   Cabal/src/Distribution/Simple/Setup/Copy.hs
	modified:   Cabal/src/Distribution/Simple/Setup/Global.hs
	modified:   Cabal/src/Distribution/Simple/Setup/Haddock.hs
	modified:   Cabal/src/Distribution/Simple/Setup/Hscolour.hs
	modified:   Cabal/src/Distribution/Simple/Setup/Install.hs
	modified:   Cabal/src/Distribution/Simple/Setup/Register.hs
	modified:   Cabal/src/Distribution/Simple/Setup/Repl.hs
	modified:   Cabal/src/Distribution/Simple/Setup/SDist.hs
	modified:   Cabal/src/Distribution/Simple/Setup/Test.hs
	modified:   Cabal/src/Distribution/Utils/MapAccum.hs
	modified:   Cabal/src/Distribution/Utils/Progress.hs
	modified:   cabal-install/src/Distribution/Client/Check.hs
	modified:   cabal-install/src/Distribution/Client/CmdOutdated.hs
	modified:   cabal-install/src/Distribution/Client/CmdPath.hs
	modified:   cabal-install/src/Distribution/Client/Configure.hs
	modified:   cabal-install/src/Distribution/Client/FileMonitor.hs
	modified:   cabal-install/src/Distribution/Client/GenBounds.hs
	modified:   cabal-install/src/Distribution/Client/IndexUtils.hs
	modified:   cabal-install/src/Distribution/Client/Main.hs
	modified:   cabal-install/src/Distribution/Client/Manpage.hs
	modified:   cabal-install/src/Distribution/Client/ProjectBuilding.hs
	modified:   cabal-install/src/Distribution/Client/ProjectConfig.hs
	modified:   cabal-install/src/Distribution/Client/Sandbox.hs
	modified:   cabal-install/src/Distribution/Client/Security/HTTP.hs
	modified:   cabal-install/src/Distribution/Deprecated/ParseUtils.hs
	modified:   cabal-install/src/Distribution/Deprecated/ReadP.hs
	modified:   cabal-install/tests/UnitTests/Distribution/Client/FileMonitor.hs
	modified:   cabal-install/tests/UnitTests/Distribution/Client/Glob.hs
	modified:   cabal-install/tests/UnitTests/Distribution/Client/UserConfig.hs
	modified:   cabal-install/tests/UnitTests/Distribution/Solver/Modular/QuickCheck.hs
	modified:   cabal-install/tests/UnitTests/Distribution/Solver/Types/OptionalStanza.hs
	modified:   cabal-testsuite/main/cabal-tests.hs
	modified:   cabal-testsuite/src/Test/Cabal/TestCode.hs

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   Cabal-syntax/src/Distribution/Compat/Binary.hs
	both modified:   Cabal-syntax/src/Distribution/Utils/Generic.hs
	both modified:   cabal-install/src/Distribution/Client/CmdUpdate.hs
	both modified:   cabal-install/src/Distribution/Client/InstallSymlink.hs
	both modified:   cabal-install/src/Distribution/Client/Targets.hs

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