More compact windows CI file (#1869) #873

Job	Run time
install (dev, Ubuntu, ubuntu-latest, 4.09.1)	41m 28s
install (dev, macOS, macos-latest, 4.14.2)	33m 18s
install (dev, Windows, windows-latest, 4.11.1, -async-proofs-j 1, opam-repository-mingw: https://...	1h 38m 24s
install (8.19.0, Ubuntu, ubuntu-latest, 4.09.1)	40m 35s
install (8.19.0, macOS, macos-latest, 4.14.2)	35m 0s
install (8.19.0, Windows, windows-latest, 4.11.1, -async-proofs-j 1, opam-repository-mingw: https...	1h 37m 2s
install (8.18.0, Ubuntu, ubuntu-latest, 4.09.1)	42m 53s
install (8.18.0, macOS, macos-latest, 4.14.2)	33m 45s
install (8.18.0, Windows, windows-latest, 4.11.1, -async-proofs-j 1, opam-repository-mingw: https...	1h 43m 4s
	8h 45m 29s

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