Use Iterator from the prelude #568

Job	Run time
loom	3m 30s
minrust	3m 30s
cross (i686-unknown-linux-gnu)	35s
miri	7m 40s
cross (armv7-unknown-linux-gnueabihf)	30s
nightly	4m 30s
cross (powerpc-unknown-linux-gnu)	33s
rustfmt	5s
cross (powerpc64-unknown-linux-gnu)	30s
stable (ubuntu-latest)	1m 6s
cross (wasm32-unknown-unknown)	6s
tsan	3m 51s
stable (macos-latest)	3m 24s
stable (windows-latest)	2m 10s
Publish Documentation	3m 18s
	35m 18s

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