ci: Bump Emacs 29.x to 3 #22

Job	Run time
test (ubuntu-latest, 26.3, false)	34s
test (ubuntu-latest, 27.2, false)	31s
test (ubuntu-latest, 28.2, false)	33s
test (ubuntu-latest, 29.3, false)	32s
test (macos-latest, 26.3, false)	1m 39s
test (macos-latest, 27.2, false)	1m 42s
test (macos-latest, 28.2, false)	2m 16s
test (macos-latest, 29.3, false)	2m 6s
test (windows-latest, 26.3, false)	1m 47s
test (windows-latest, 27.2, false)	1m 4s
test (windows-latest, 28.2, false)	1m 1s
test (windows-latest, 29.3, false)	43s
test (ubuntu-latest, snapshot, true)	26s
test (macos-latest, snapshot, true)	1m 34s
test (windows-latest, snapshot, true)	31s
	16m 59s

Provide feedback