Update supported GitHub Enterprise Server versions #6871

Job	Run time
Split workflow (ubuntu-latest, linked)	1m 51s
Split workflow (macos-latest, default)	1m 47s
Split workflow (macos-latest, nightly-latest)	1m 49s
Split workflow (macos-latest, linked)	1m 8s
Split workflow (ubuntu-latest, default)	1m 24s
Split workflow (ubuntu-latest, nightly-latest)	1m 37s
	9m 36s

Provide feedback