update MSRV #31

Job	Run time
rustfmt	23s
Test stable on ubuntu-latest ()	36s
Test stable on ubuntu-latest (--no-default-features)	30s
Test nightly on ubuntu-latest ()	20s
Test nightly on ubuntu-latest (--no-default-features)	23s
Test stable on macos-latest ()	49s
Test stable on macos-latest (--no-default-features)	49s
Test nightly on macos-latest ()	1m 4s
Test nightly on macos-latest (--no-default-features)	1m 11s
Test stable on windows-latest ()	1m 50s
Test stable on windows-latest (--no-default-features)	1m 48s
Test nightly on windows-latest ()	57s
Test nightly on windows-latest (--no-default-features)	1m 6s
clippy	15s
Test 1.60 on ubuntu-latest ()	3m 19s
Test 1.60 on ubuntu-latest (--no-default-features)	2m 42s
Test 1.60 on macos-latest ()	49s
Test 1.60 on macos-latest (--no-default-features)	40s
Test 1.60 on windows-latest ()	3m 38s
Test 1.60 on windows-latest (--no-default-features)	4m 14s
	27m 23s

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