ci: Remove macos-13 runner #1061

Job	Run time
build-and-test (macos-15, 16.4, false, true, true) / build-and-test	20m 18s
build-and-test (macos-14, 15.4, true, vimtags, check-xcodeproj-compat) / build-and-test	15m 0s
build-and-test (macos-13-xcode14-self-hosted, true, _10.9, true, true) / build-and-test	0s
	35m 18s

Provide feedback