Remove old checks #1

Job	Run time
ruby-versions / Generate Ruby versions	3s
test (2.5, ubuntu-latest)	30s
test (2.5, macos-latest)	56s
test (2.5, windows-latest)	3m 2s
test (2.6, ubuntu-latest)	32s
test (2.6, macos-latest)	1m 45s
test (2.6, windows-latest)	2m 55s
test (2.7, ubuntu-latest)	37s
test (2.7, macos-latest)	1m 7s
test (2.7, windows-latest)	2m 5s
test (3.0, ubuntu-latest)	24s
test (3.0, macos-latest)	29s
test (3.0, windows-latest)	1m 40s
test (3.1, ubuntu-latest)	30s
test (3.1, macos-latest)	36s
test (3.1, windows-latest)	1m 31s
test (3.2, ubuntu-latest)	25s
test (3.2, macos-latest)	35s
test (3.2, windows-latest)	2m 36s
test (head, ubuntu-latest)	28s
test (head, macos-latest)	35s
test (head, windows-latest)	2m 17s
test (jruby, ubuntu-latest)	3m 11s
test (jruby-head, ubuntu-latest)	3m 12s
test (truffleruby, ubuntu-latest)	2m 15s
test (truffleruby-head, ubuntu-latest)	3m 10s
	37m 26s

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