fix: revert MSRV changes #2116

Job	Run time
docs	34s
check no_std	47s
clippy	50s
features stable	2m 18s
features stable --all-targets	3m 31s
fmt	12s
miri --no-default-features	5m 2s
features nightly	1m 51s
features nightly --all-targets	3m 9s
miri	4m 55s
test ubuntu-latest stable --no-default-features	1m 18s
wasm	41s
miri --all-features	7m 9s
test ubuntu-latest stable	1m 21s
test ubuntu-latest nightly --no-default-features	1m 1s
test ubuntu-latest nightly	56s
test ubuntu-latest 1.79 --no-default-features	39s
test ubuntu-latest 1.79	38s
test windows-latest stable --no-default-features	2m 48s
test windows-latest stable	2m 53s
test windows-latest nightly --no-default-features	2m 17s
test windows-latest nightly	2m 17s
test windows-latest 1.79 --no-default-features	1m 49s
test windows-latest 1.79	1m 27s
test ubuntu-latest 1.79 --features json	43s
test windows-latest 1.79 --features json	1m 19s
test ubuntu-latest nightly --all-features	1m 14s
test windows-latest nightly --all-features	2m 32s
	56m 11s

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