Remove redundant reserve call (#674) #578

Job	Run time
loom	3m 34s
cross (i686-unknown-linux-gnu)	26s
minrust	3m 28s
cross (armv7-unknown-linux-gnueabihf)	1m 11s
miri	7m 50s
cross (powerpc-unknown-linux-gnu)	31s
nightly	4m 55s
cross (powerpc64-unknown-linux-gnu)	1m 5s
rustfmt	10s
cross (wasm32-unknown-unknown)	47s
stable (ubuntu-latest)	1m 7s
stable (macos-latest)	1m 44s
tsan	3m 53s
stable (windows-latest)	2m 24s
Publish Documentation	3m 21s
	36m 26s

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