Prepare 21.2.1 release. #1459

Job	Run time
mypy	25s
ruff	8s
sdist	1m 3s
parse_sdl (macos-latest, 3.2.16)	33s
parse_sdl (windows-latest, 3.2.16)	52s
test-docs	2m 5s
pyodide	2m 26s
build-macos (cp314t-*_universal2)	2m 22s
build-macos (cp310-*_universal2)	1m 56s
tox (ubuntu-latest)	2m 5s
build-macos (pp311-*)	3m 57s
linux-wheels (x86_64, cp310-manylinux*)	4m 14s
linux-wheels (aarch64, cp310-manylinux*)	4m 3s
linux-wheels (aarch64, pp311-manylinux*)	3m 29s
linux-wheels (aarch64, cp314t-manylinux*)	3m 49s
linux-wheels (x86_64, cp314t-manylinux*)	8m 26s
linux-wheels (x86_64, pp311-manylinux*)	3m 31s
build (windows-latest, 3.10, x86)	3m 31s
build (windows-latest, 3.10, x64)	2m 40s
build (ubuntu-latest, 3.14t, x64)	4m 9s
build (windows-latest, pypy-3.10, x64)	4m 26s
build (windows-latest, 3.14t, x64)	3m 17s
build (ubuntu-latest, 3.10, x64)	3m 41s
build (windows-latest, 3.14t, x86)	3m 40s
build (windows-11-arm, 3.14t, arm64)	4m 9s
build (windows-11-arm, 3.11, arm64)	4m 27s
build (ubuntu-latest, pypy-3.10, x64)	3m 7s
publish	0s
	1h 22m 31s

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