Update itertools requirement from 0.12.0 to 0.13.0 (#280) #526

Job	Run time
check_features (ubuntu, --features serde)	25s
tests (windows, x86_64-pc-windows-msvc)	5m 10s
tests (windows, i686-pc-windows-msvc)	3m 49s
check_features (ubuntu, --features datasets)	19s
check_features (ubuntu)	2m 37s
tests (ubuntu, x86_64-unknown-linux-gnu)	4m 17s
tests (ubuntu, i686-unknown-linux-gnu)	3m 7s
tests (ubuntu, wasm32-unknown-unknown)	4m 52s
tests (macos, aarch64-apple-darwin)	4m 13s
tests (ubuntu, wasm32-wasi)	3m 49s
	32m 38s

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