CI: Use a Ubuntu 20.04 container to keep Ubuntu 20.04 support #1977

Job	Run time
build-spidermonkey-win	12s
build-spidermonkey-unix (macos-13, 3.10)	9s
build-spidermonkey-unix (ubuntu-22.04-arm, 3.10)	10s
build-spidermonkey-unix (ubuntu-22.04, 3.10)	11s
sdist	35s
build-spidermonkey-unix (macos-14, 3.10)	7s
build-and-test (ubuntu-22.04, 3.8)	4m 5s
build-and-test (ubuntu-22.04, 3.13)	3m 55s
build-and-test (ubuntu-22.04, 3.11)	3m 55s
build-and-test (ubuntu-22.04, 3.10)	3m 29s
build-and-test (macos-13, 3.10)	4m 18s
build-and-test (ubuntu-22.04, 3.12)	4m 17s
build-and-test (macos-13, 3.11)	3m 41s
build-and-test (macos-13, 3.8)	4m 16s
build-and-test (ubuntu-22.04, 3.9)	4m 4s
build-and-test (macos-13, 3.13)	4m 15s
build-and-test (macos-13, 3.9)	3m 44s
build-and-test (macos-14, 3.8)	3m 19s
build-and-test (macos-14, 3.11)	2m 16s
build-and-test (macos-14, 3.10)	3m 15s
build-and-test (macos-14, 3.9)	3m 3s
build-and-test (windows-2022, 3.9)	6m 19s
build-and-test (macos-13, 3.12)	5m 16s
build-and-test (windows-2022, 3.13)	8m 28s
build-and-test (macos-14, 3.12)	2m 29s
build-and-test (windows-2022, 3.12)	5m 28s
build-and-test (windows-2022, 3.11)	6m 35s
build-and-test (windows-2022, 3.8)	6m 29s
build-and-test (ubuntu-22.04-arm, 3.9)	3m 58s
build-and-test (ubuntu-22.04-arm, 3.8)	4m 0s
build-and-test (macos-14, 3.13)	2m 59s
build-and-test (windows-2022, 3.10)	6m 24s
build-and-test (ubuntu-22.04-arm, 3.13)	4m 8s
build-and-test (ubuntu-22.04-arm, 3.10)	3m 59s
build-and-test (ubuntu-22.04-arm, 3.12)	4m 12s
build-and-test (ubuntu-22.04-arm, 3.11)	4m 25s
publish-nightly	0s
publish-archive	0s
publish	0s
	2h 12m 25s

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