Fix double spaces in comments and doc comments #706

Job	Run time
miri	11m 3s
minrust	2m 27s
cross (i686-unknown-linux-gnu)	40s
loom	2m 33s
cross (armv7-unknown-linux-gnueabihf)	34s
nightly	3m 48s
cross (powerpc-unknown-linux-gnu)	25s
rustfmt	4s
cross (powerpc64-unknown-linux-gnu)	27s
cross (wasm32-unknown-unknown)	7s
stable (ubuntu-latest)	1m 26s
tsan	3m 51s
stable (macos-latest)	1m 4s
stable (windows-latest)	2m 47s
Publish Documentation	2m 23s
	33m 39s

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