Prepare 21.1.0 release. #1433

Job	Run time
ruff	6s
sdist	2m 0s
mypy	25s
parse_sdl (windows-latest, 3.2.16)	1m 3s
parse_sdl (macos-latest, 3.2.16)	26s
test-docs	2m 15s
build-macos (cp310-*_universal2)	1m 51s
build-macos (cp314t-*_universal2)	2m 48s
tox (ubuntu-latest)	3m 25s
pyodide	3m 21s
build-macos (pp310-*)	3m 37s
linux-wheels (x86_64, cp310-manylinux*)	4m 11s
linux-wheels (aarch64, cp314t-manylinux*)	4m 14s
linux-wheels (aarch64, pp310-manylinux*)	3m 27s
linux-wheels (x86_64, pp310-manylinux*)	3m 49s
linux-wheels (x86_64, cp314t-manylinux*)	4m 42s
linux-wheels (aarch64, cp310-manylinux*)	4m 10s
build (windows-latest, 3.10, x64)	2m 39s
build (windows-latest, 3.14t, x86)	4m 25s
build (windows-latest, 3.14t, x64)	3m 11s
build (windows-latest, 3.10, x86)	4m 9s
build (windows-latest, pypy-3.10, x64)	3m 33s
build (windows-11-arm, 3.11, arm64)	4m 38s
build (ubuntu-latest, 3.14t, x64)	5m 22s
build (windows-11-arm, 3.14t, arm64)	4m 33s
build (ubuntu-latest, 3.10, x64)	5m 23s
build (ubuntu-latest, pypy-3.10, x64)	4m 49s
publish	1m 6s
	1h 29m 38s

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