Update coq-alpine.yml #1000

Job	Run time
install (dev, macOS, macos-latest, 4.14.2)	36m 15s
install (8.20.0, macOS, macos-latest, 4.14.2)	31m 46s
install (8.20.0, Ubuntu, ubuntu-latest, 4.09.1)	40m 16s
install (8.19.0, macOS, macos-latest, 4.14.2)	35m 32s
install (dev, Ubuntu, ubuntu-latest, 4.09.1)	39m 43s
install (dev, Windows, windows-latest, 4.13.1, -async-proofs-j 1, git+https://github.com/ocaml/oc...	1h 31m 34s
install (8.20.0, Windows, windows-latest, 4.13.1, -async-proofs-j 1, git+https://github.com/ocaml...	1h 35m 23s
install (8.18.0, Ubuntu, ubuntu-latest, 4.09.1)	42m 18s
install (8.19.0, Windows, windows-latest, 4.13.1, -async-proofs-j 1, git+https://github.com/ocaml...	1h 35m 28s
install (8.18.0, Windows, windows-latest, 4.13.1, -async-proofs-j 1, git+https://github.com/ocaml...	1h 39m 41s
install (8.18.0, macOS, macos-latest, 4.14.2)	36m 52s
install (8.19.0, Ubuntu, ubuntu-latest, 4.09.1)	41m 10s
	11h 25m 58s

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