Use -D warnings instead of deny-warnings feature.

[Jarcho]

r? @flip1995
changelog: none

[flip1995]

failures:
    test_no_deps_ignores_path_deps_in_workspaces

Oh, this is a good catch. path_dep should be changed to trigger a Clippy lint, not a rustc lint.

Ah nevermind. But that feature should be registered in the Cargo.toml of the path_dep package.

[flip1995]

@bors r+

Thanks!

[bors]

📌 Commit 4e57b2c has been approved by flip1995

It is now in the queue for this repository.

[bors]

⌛ Testing commit 4e57b2c with merge 9d9a0dc...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: flip1995
Pushing 9d9a0dc to master...