Update supported GitHub Enterprise Server versions #7124

Job	Run time
Split workflow (ubuntu-latest, default)	1m 36s
Split workflow (macos-latest, linked)	1m 13s
Split workflow (ubuntu-latest, linked)	1m 7s
Split workflow (macos-latest, default)	1m 31s
Split workflow (ubuntu-latest, nightly-latest)	1m 13s
Split workflow (macos-latest, nightly-latest)	1m 12s
	7m 52s

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