drop support for macOS 12 #770

Job	Run time
docker-master	1h 29m 11s
publish-standalone-dry-run	14s
test-standalone (master, dev, default)	1m 32s
build-js-of-ocaml (master, 4.11.1)	5m 55s
build-wasm-of-ocaml (master, 4.14.1)	16m 55s
standalone-haskell (master)	46m 47s
generated-files (master)	30s
test-amd64	2h 18m 20s
validate-docker-master	21m 38s
deploy-js-wasm-of-ocaml	1m 23s
docker-check-all	4s
	5h 22m 29s

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