Document + ?Sized in a few more places #533

Job	Run time
clippy/stable	22s
Pass MSRV values to other jobs	3s
nostd/thumbv6m-none-eabi/stable	21s
miri	11m 18s
cross_test/s390x-unknown-linux-gnu/stable	2m 0s
cargo-careful	1m 56s
cross_test/i686-unknown-linux-gnu/stable	1m 45s
format/nightly	13s
docs/nightly	23s
blas-msrv	52s
tests/beta	2m 16s
tests/nightly	2m 31s
tests/stable	2m 32s
tests/1.64.0	2m 31s
conclusion	-1s
	29m 2s

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