Pin sklearn version #138

Job	Run time
run-tests (local, windows-latest, 3.9)	10m 23s
run-tests (local, windows-latest, 3.10)	7m 8s
run-tests (local, windows-latest, 3.11)	5m 21s
run-tests (local, windows-latest, 3.12)	6m 15s
run-tests (local, ubuntu-latest, 3.9)	11m 54s
run-tests (local, ubuntu-latest, 3.10)	10m 45s
run-tests (local, ubuntu-latest, 3.11)	10m 34s
run-tests (local, ubuntu-latest, 3.12)	10m 53s
run-tests (local, macos-13, 3.9)	21m 3s
run-tests (local, macos-13, 3.10)	16m 28s
run-tests (local, macos-13, 3.11)	25m 26s
run-tests (local, macos-13, 3.12)	15m 17s
	2h 31m 27s

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