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Document + ?Sized in a few more places #534

Job	Run time
cargo-careful	2m 4s
Pass MSRV values to other jobs	4s
cross_test/s390x-unknown-linux-gnu/stable	8m 17s
clippy/stable	21s
cross_test/i686-unknown-linux-gnu/stable	1m 57s
format/nightly	15s
miri	9m 42s
nostd/thumbv6m-none-eabi/stable	19s
docs/nightly	23s
blas-msrv	53s
tests/nightly	2m 41s
tests/beta	2m 28s
tests/stable	2m 29s
tests/1.64.0	3m 23s
conclusion	2s
	35m 18s