ci: Bump Emacs 29.x to 4 #4

Job	Run time
build (ubuntu-latest, 26.3, false)	36s
build (ubuntu-latest, 27.2, false)	36s
build (ubuntu-latest, 28.2, false)	33s
build (ubuntu-latest, 29.4, false)	44s
build (macos-latest, 26.3, false)	50s
build (macos-latest, 27.2, false)	52s
build (macos-latest, 28.2, false)	1m 21s
build (macos-latest, 29.4, false)	1m 26s
build (windows-latest, 26.3, false)	1m 38s
build (windows-latest, 27.2, false)	1m 11s
build (windows-latest, 28.2, false)	54s
build (windows-latest, 29.4, false)	1m 12s
build (ubuntu-latest, snapshot, true)	31s
build (macos-latest, snapshot, true)	1m 21s
build (windows-latest, snapshot, true)	39s
	14m 24s

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