chore(ci): pin tokio in msrv job #2776

Job	Run time
Verify hyper.h is up to date	27s
Check Style	10s
semver	19s
Test with Miri	2m 2s
Test stable on ubuntu-latest	1m 7s
Test stable on windows-latest	1m 54s
Test C API (FFI)	21s
features	38s
Test stable on macOS-latest	1m 11s
minimal-versions	36s
Test beta on ubuntu-latest	1m 9s
Check MSRV	43s
Test beta on windows-latest	1m 51s
udeps	23s
Test beta on macOS-latest	1m 10s
Test nightly on ubuntu-latest	1m 5s
Test nightly on windows-latest	2m 14s
Test nightly on macOS-latest	1m 12s
Build docs	13s
Check exposed types	16s
CI is green	1s
	19m 2s

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