chore(tokio): warn on dead code #535

Job	Run time
semver	2m 35s
Check Style	14s
Test with Miri	47s
Check MSRV (1.63)	2m 37s
Test stable on ubuntu-latest	35s
features	45s
Test stable on windows-latest	1m 31s
Test stable on macos-latest	35s
Test beta on ubuntu-latest	33s
Test beta on windows-latest	1m 27s
Test beta on macos-latest	52s
Test nightly on ubuntu-latest	32s
Test nightly on windows-latest	1m 8s
Test nightly on macos-latest	42s
Build docs	14s
CI is green	1s
	15m 8s

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