Update to Python 3.15b3 #15572

Job	Run time
stubtest: stdlib (windows-latest, 3.14)	2m 6s
stubtest: stdlib (windows-latest, 3.15)	2m 0s
stubtest: stdlib (ubuntu-latest, 3.13)	36s
stubtest: stdlib (macos-latest, 3.12)	48s
stubtest: stdlib (ubuntu-latest, 3.11)	34s
stubtest: stdlib (ubuntu-latest, 3.15)	52s
stubtest: stdlib (macos-latest, 3.14)	1m 1s
stubtest: stdlib (macos-latest, 3.13)	46s
stubtest: stdlib (macos-latest, 3.11)	30s
stubtest: stdlib (macos-latest, 3.10)	47s
stubtest: stdlib (windows-latest, 3.13)	1m 5s
stubtest: stdlib (ubuntu-latest, 3.12)	33s
stubtest: stdlib (ubuntu-latest, 3.14)	41s
stubtest: stdlib (windows-latest, 3.12)	1m 22s
stubtest: stdlib (ubuntu-latest, 3.10)	44s
stubtest: stdlib (windows-latest, 3.11)	2m 8s
stubtest: stdlib (macos-latest, 3.15)	1m 8s
	17m 41s

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