chore(ci): pin tokio-util in MSRV CI job #474

Job	Run time
Check Style	5s
semver	2m 39s
Test with Miri	47s
Check MSRV (1.63)	1m 56s
features	42s
Test stable on ubuntu-latest	44s
Test stable on windows-latest	2m 38s
Test stable on macos-latest	30s
Test beta on ubuntu-latest	33s
Test beta on windows-latest	1m 23s
Test beta on macos-latest	36s
Test nightly on ubuntu-latest	35s
Test nightly on windows-latest	1m 14s
Test nightly on macos-latest	45s
Build docs	13s
CI is green	1s
	15m 21s

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