CI: Use a Ubuntu 20.04 container to keep Ubuntu 20.04 support #1974

Job	Run time
build-spidermonkey-win	12s
sdist	31s
build-spidermonkey-unix (macos-13, 3.10)	8s
build-spidermonkey-unix (ubuntu-22.04-arm, 3.10)	9s
build-spidermonkey-unix (ubuntu-22.04, 3.10)	7s
build-spidermonkey-unix (macos-14, 3.10)	5s
build-and-test (ubuntu-22.04, 3.9)	3m 57s
build-and-test (ubuntu-22.04, 3.8)	4m 9s
build-and-test (macos-13, 3.8)	3m 54s
build-and-test (ubuntu-22.04, 3.10)	4m 9s
build-and-test (ubuntu-22.04, 3.11)	4m 43s
build-and-test (ubuntu-22.04, 3.13)	4m 51s
build-and-test (macos-13, 3.10)	4m 56s
build-and-test (ubuntu-22.04, 3.12)	4m 11s
build-and-test (macos-14, 3.9)	3m 17s
build-and-test (macos-13, 3.12)	4m 53s
build-and-test (macos-13, 3.11)	3m 56s
build-and-test (macos-13, 3.9)	5m 1s
build-and-test (macos-14, 3.8)	3m 1s
build-and-test (windows-2022, 3.13)	7m 22s
build-and-test (macos-14, 3.11)	3m 14s
build-and-test (windows-2022, 3.8)	6m 58s
build-and-test (windows-2022, 3.9)	7m 32s
build-and-test (macos-13, 3.13)	3m 54s
build-and-test (macos-14, 3.12)	3m 9s
build-and-test (macos-14, 3.10)	2m 31s
build-and-test (ubuntu-22.04-arm, 3.11)	5m 9s
build-and-test (windows-2022, 3.12)	7m 14s
build-and-test (ubuntu-22.04-arm, 3.8)	4m 37s
build-and-test (windows-2022, 3.10)	5m 40s
build-and-test (windows-2022, 3.11)	7m 11s
build-and-test (ubuntu-22.04-arm, 3.12)	3m 49s
build-and-test (ubuntu-22.04-arm, 3.10)	5m 4s
build-and-test (macos-14, 3.13)	2m 21s
build-and-test (ubuntu-22.04-arm, 3.9)	3m 44s
build-and-test (ubuntu-22.04-arm, 3.13)	3m 24s
publish-nightly	-1s
publish-archive	-1s
publish	-1s
	2h 19m 0s

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