build

Update core-test submodule & Drop Emacs 26 support #333

Job	Run time
test (ubuntu-latest, 28.2, false)	49s
test (ubuntu-latest, 29.3, false)	1m 45s
test (macos-latest, 28.2, false)	1m 52s
test (macos-latest, 29.3, false)	1m 59s
test (windows-latest, 28.2, false)	1m 11s
test (windows-latest, 29.3, false)	1m 24s
test (ubuntu-latest, 26.3, false)	46s
test (windows-latest, 26.3, false)	2m 32s
test (ubuntu-latest, 27.2, false)	51s
test (windows-latest, 27.2, false)	1m 26s
test (ubuntu-latest, snapshot, true)	43s
test (macos-latest, snapshot, true)	1m 31s
test (windows-latest, snapshot, true)	1m 56s
	18m 45s

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