ci: Bump Emacs 29.x to 4 #77

Job	Run time
build (ubuntu-latest, 26.3, false)	3m 8s
build (ubuntu-latest, 27.2, false)	48s
build (ubuntu-latest, 28.2, false)	1m 1s
build (ubuntu-latest, 29.4, false)	59s
build (macos-latest, 26.3, false)	1m 8s
build (macos-latest, 27.2, false)	1m 20s
build (macos-latest, 28.2, false)	1m 14s
build (macos-latest, 29.4, false)	1m 20s
build (windows-latest, 26.3, false)	2m 31s
build (windows-latest, 27.2, false)	1m 55s
build (windows-latest, 28.2, false)	3m 51s
build (windows-latest, 29.4, false)	4m 3s
build (ubuntu-latest, snapshot, true)	45s
build (macos-latest, snapshot, true)	1m 12s
build (windows-latest, snapshot, true)	1m 38s
	26m 53s

Provide feedback