Drop 3.9 support in the stdlib #15092

Job	Run time
stubtest: stdlib (ubuntu-latest, 3.12)	31s
stubtest: stdlib (windows-latest, 3.11)	1m 28s
stubtest: stdlib (ubuntu-latest, 3.14)	43s
stubtest: stdlib (windows-latest, 3.13)	1m 18s
stubtest: stdlib (ubuntu-latest, 3.13)	41s
stubtest: stdlib (macos-latest, 3.14)	31s
stubtest: stdlib (macos-latest, 3.10)	59s
stubtest: stdlib (macos-latest, 3.12)	45s
stubtest: stdlib (macos-latest, 3.13)	25s
stubtest: stdlib (ubuntu-latest, 3.10)	42s
stubtest: stdlib (windows-latest, 3.14)	1m 27s
stubtest: stdlib (ubuntu-latest, 3.11)	35s
stubtest: stdlib (windows-latest, 3.12)	1m 25s
stubtest: stdlib (macos-latest, 3.11)	35s
	12m 5s

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