doc: update `zerocopy` feature docs again #93

Job	Run time
clippy-benches	24s
format	5s
semver	15s
clippy (1.64.0, --no-default-features)	2m 49s
test	2m 29s
clippy (stable, --no-default-features)	13s
clippy (nightly, --all-features, --tests)	28s
	6m 43s

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