Clearly document SegQueue is FIFO (#1144) #3035

Job	Run time
codegen	30s
dependencies	16s
features (msrv)	1m 1s
test (1.61, ubuntu-latest)	11m 20s
features (nightly)	23s
test (1.61, windows-latest)	15m 47s
careful	4m 46s
clippy	14s
test (stable, ubuntu-latest)	9m 36s
docs	13s
test (stable, windows-latest)	14m 20s
loom	53s
test (nightly, ubuntu-latest)	8m 45s
miri	1h 55m 59s
test (nightly, windows-latest)	13m 14s
rustfmt	3s
test (nightly, ubuntu-latest, i686-unknown-linux-gnu)	9m 47s
san	12m 46s
shellcheck	8s
test (nightly, ubuntu-latest, armv7-unknown-linux-gnueabihf)	14m 42s
test (nightly, ubuntu-latest, armv5te-unknown-linux-gnueabi)	16m 9s
	4h 10m 52s

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