Prepare 4.15 release (#2523) #8138

Job	Run time
CPython 3.9-ubuntu-latest	11m 30s
static	3m 21s
DocTest	1m 4s
CPython 3.13t-ubuntu-latest	11m 46s
CPython pypy-3.10-ubuntu-latest	12m 22s
Link Check	1m 38s
Typing Tests (3.9)	1m 0s
Make an sdist	15s
Test async's minimum dependencies and Python	41s
Docs Checks	47s
Test using minimum dependencies and supported Python	35s
Typing Tests (3.11)	1m 4s
Install from SDist and Test	1m 9s
	47m 12s

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