ci: Use macos-12 #3033

Job	Run time
test (stable)	2m 59s
test (no rustup)	1m 50s
test (beta)	2m 58s
test (nightly)	2m 48s
test (1.26)	6m 6s
test (nightly, macos-latest)	2m 49s
test (1.30)	4m 7s
test (1.31)	4m 18s
test (nightly, windows-latest)	4m 23s
test (1.36)	4m 59s
test (1.39)	4m 50s
test (1.41)	4m 50s
miri / miri	58s
deny / deny	15s
msrv / msrv	3m 0s
release-dry-run / prepare	5s
tidy / tidy	57s
release-dry-run / build (aarch64-unknown-linux-gnu)	1m 11s
release-dry-run / build (aarch64-unknown-linux-musl)	46s
release-dry-run / build (aarch64-apple-darwin, macos-12)	1m 2s
release-dry-run / build (aarch64-pc-windows-msvc, windows-2019)	2m 23s
release-dry-run / build (x86_64-unknown-linux-gnu)	35s
release-dry-run / build (x86_64-unknown-linux-musl)	41s
release-dry-run / build (x86_64-apple-darwin, macos-12)	59s
release-dry-run / build (x86_64-pc-windows-msvc, windows-2019)	1m 40s
release-dry-run / build (x86_64-unknown-freebsd)	1m 8s
release-dry-run / build (universal-apple-darwin, macos-12)	1m 10s
	1h 3m 47s

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