Relax MSRV of utils to 1.56 #3104

Job	Run time
dependencies	16s
test (1.63, ubuntu-latest)	11m 37s
test (1.63, windows-latest)	15m 59s
clippy	16s
test (stable, ubuntu-latest)	10m 13s
codegen	3s
careful	5m 11s
test (stable, windows-latest)	13m 51s
test (nightly, ubuntu-latest)	9m 33s
docs	11s
test (nightly, windows-latest)	13m 15s
features (msrv)	53s
loom	57s
test (nightly, ubuntu-latest, i686-unknown-linux-gnu)	10m 39s
features (nightly)	22s
miri (channel)	22m 37s
test (nightly, ubuntu-latest, armv7-unknown-linux-gnueabihf)	15m 30s
miri (others)	14m 36s
rustfmt	5s
test (nightly, ubuntu-latest, armv5te-unknown-linux-gnueabi)	16m 45s
san	13m 33s
shellcheck	6s
	2h 56m 28s

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