chore: address MSRV TODOs for 1.81 (#781) #2104

Job	Run time
clippy	1m 14s
docs	52s
check no_std	46s
features stable	2m 9s
fmt	12s
features stable --all-targets	3m 40s
miri --no-default-features	5m 7s
miri	5m 6s
features nightly	2m 26s
miri --all-features	6m 56s
wasm	31s
features nightly --all-targets	3m 32s
test ubuntu-latest stable --no-default-features	1m 12s
test ubuntu-latest stable	1m 13s
test ubuntu-latest nightly --no-default-features	1m 17s
test ubuntu-latest nightly	1m 13s
test ubuntu-latest 1.81 --no-default-features	39s
test ubuntu-latest 1.81	44s
test windows-latest stable --no-default-features	2m 59s
test windows-latest stable	2m 40s
test windows-latest nightly --no-default-features	2m 51s
test windows-latest nightly	3m 10s
test windows-latest 1.81 --no-default-features	1m 26s
test windows-latest 1.81	1m 48s
test ubuntu-latest 1.81 --features json	45s
test windows-latest 1.81 --features json	1m 50s
test ubuntu-latest nightly --all-features	1m 26s
test windows-latest nightly --all-features	3m 16s
	1h 1m 0s

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