Prepare 21.2.0 release. #1437

Job	Run time
mypy	23s
ruff	6s
sdist	54s
parse_sdl (macos-latest, 3.2.16)	29s
parse_sdl (windows-latest, 3.2.16)	41s
test-docs	2m 11s
pyodide	2m 37s
tox (ubuntu-latest)	2m 14s
build-macos (cp310-*_universal2)	1m 54s
build-macos (pp310-*)	3m 42s
build-macos (cp314t-*_universal2)	2m 21s
linux-wheels (aarch64, pp310-manylinux*)	3m 29s
linux-wheels (aarch64, cp310-manylinux*)	4m 2s
linux-wheels (x86_64, pp310-manylinux*)	3m 47s
linux-wheels (x86_64, cp310-manylinux*)	4m 4s
linux-wheels (x86_64, cp314t-manylinux*)	4m 20s
linux-wheels (aarch64, cp314t-manylinux*)	4m 5s
build (ubuntu-latest, 3.14t, x64)	3m 43s
build (ubuntu-latest, 3.10, x64)	3m 53s
build (windows-latest, 3.10, x64)	2m 41s
build (windows-latest, 3.10, x86)	4m 13s
build (ubuntu-latest, pypy-3.10, x64)	3m 4s
build (windows-latest, pypy-3.10, x64)	4m 50s
build (windows-11-arm, 3.11, arm64)	4m 6s
build (windows-11-arm, 3.14t, arm64)	5m 1s
build (windows-latest, 3.14t, x86)	4m 16s
build (windows-latest, 3.14t, x64)	3m 18s
publish	1m 8s
	1h 21m 32s

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