Clearly document SegQueue is FIFO #3015

Job	Run time
codegen	39s
features (msrv)	53s
dependencies	17s
features (nightly)	22s
test (1.61, ubuntu-latest)	11m 5s
test (1.61, windows-latest)	15m 24s
careful	4m 44s
docs	11s
test (stable, ubuntu-latest)	9m 18s
clippy	20s
test (stable, windows-latest)	13m 57s
loom	58s
test (nightly, ubuntu-latest)	8m 49s
miri	1h 59m 28s
test (nightly, windows-latest)	13m 17s
test (nightly, ubuntu-latest, i686-unknown-linux-gnu)	9m 57s
rustfmt	10s
test (nightly, ubuntu-latest, armv7-unknown-linux-gnueabihf)	14m 58s
san	12m 49s
shellcheck	7s
test (nightly, ubuntu-latest, armv5te-unknown-linux-gnueabi)	16m 11s
	4h 13m 54s

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