fix uniqueMutationsOfType() and uniqueMutations #1304

Job	Run time
tests-Windows-CLI (mingw64, x86_64, 3.8)	8m 40s
tests-Unix-CLI (ubuntu-20.04, 7, 3.8)	3m 2s
tests-Windows-CLI (ucrt64, ucrt-x86_64, 3.8)	8m 27s
canceller	4s
tests-Unix-CLI (ubuntu-20.04, 11, 3.9)	3m 2s
tests-Unix-GUI (ubuntu-20.04, 5.9.5, 7)	2m 9s
tests-Unix-CLI (macos-12, 3.8)	4m 10s
tests-Unix-GUI (ubuntu-20.04, 5.15.2, 11)	2m 43s
tests-Windows-GUI (mingw64, x86_64)	5m 42s
tests-Unix-CLI (macos-13, 3.9)	4m 54s
tests-windows-latest-pacman (mingw64, x86_64)	1m 48s
tests-Unix-GUI (ubuntu-22.04, 5.15.2, 12)	2m 23s
tests-Windows-GUI (ucrt64, ucrt-x86_64)	5m 35s
tests-windows-latest-pacman (ucrt64, ucrt-x86_64)	1m 46s
tests-Unix-GUI (ubuntu-22.04, 6.7.2, 12)	2m 25s
tests-Unix-GUI (macos-12, 5.9.5)	2m 34s
tests-Unix-GUI (macos-13, 5.15.2)	3m 12s
tests-Unix-GUI (macos-13, 6.7.2)	4m 48s
	1h 7m 24s

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