CI: Use a Ubuntu 20.04 container to keep Ubuntu 20.04 support #1968

Job	Run time
build-spidermonkey-win	13s
sdist	35s
build-spidermonkey-unix (macos-13, 3.10)	10s
build-spidermonkey-unix (macos-14, 3.10)	6s
build-spidermonkey-unix (ubuntu-22.04, 3.10)	13m 27s
build-spidermonkey-unix (ubuntu-22.04-arm, 3.10)	10s
build-and-test (ubuntu-22.04, 3.8)	7s
build-and-test (ubuntu-22.04, 3.12)	10s
build-and-test (ubuntu-22.04, 3.9)	7s
build-and-test (ubuntu-22.04, 3.11)	11s
build-and-test (ubuntu-22.04, 3.10)	9s
build-and-test (ubuntu-22.04, 3.13)	8s
build-and-test (macos-13, 3.12)	6m 49s
build-and-test (macos-14, 3.12)	2m 26s
build-and-test (macos-14, 3.9)	2m 58s
build-and-test (macos-13, 3.8)	1m 59s
build-and-test (macos-14, 3.13)	1m 29s
build-and-test (macos-13, 3.13)	3m 59s
build-and-test (macos-14, 3.8)	2m 29s
build-and-test (macos-14, 3.10)	1m 2s
build-and-test (macos-13, 3.11)	5m 2s
build-and-test (windows-2022, 3.9)	7m 23s
build-and-test (macos-13, 3.10)	6m 18s
build-and-test (windows-2022, 3.12)	5m 23s
build-and-test (macos-13, 3.9)	38s
build-and-test (windows-2022, 3.11)	7m 24s
build-and-test (ubuntu-22.04-arm, 3.9)	3m 36s
build-and-test (windows-2022, 3.8)	7m 19s
build-and-test (ubuntu-22.04-arm, 3.13)	3m 43s
build-and-test (windows-2022, 3.10)	7m 22s
build-and-test (macos-14, 3.11)	2m 32s
build-and-test (windows-2022, 3.13)	7m 34s
build-and-test (ubuntu-22.04-arm, 3.10)	4m 38s
build-and-test (ubuntu-22.04-arm, 3.11)	3m 42s
build-and-test (ubuntu-22.04-arm, 3.12)	4m 23s
build-and-test (ubuntu-22.04-arm, 3.8)	3m 39s
publish-nightly	1s
publish-archive	1s
publish	1s
	1h 59m 23s

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