Update itertools requirement from 0.12.0 to 0.13.0 #246

Job	Run time
Clippy	33s
Test	2m 53s
Build with rust 1.69.0 on Linux	1m 15s
Build with rust 1.69.0 on Windows	2m 46s
Build with rust 1.69.0 on macOS	1m 20s
Build with rust stable on Linux	1m 7s
Build with rust stable on Windows	5m 5s
Build with rust stable on macOS	53s
Build with rust beta on Linux	1m 0s
Build with rust beta on Windows	3m 33s
Build with rust beta on macOS	1m 10s
Build with rust nightly on Linux	1m 20s
Build with rust nightly on Windows	2m 11s
Build with rust nightly on macOS	57s
	26m 3s

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