Update supported GitHub Enterprise Server versions #4217

Job	Run time
Config export (windows-latest, nightly-latest)	6m 49s
Config export (macos-latest, linked)	1m 7s
Config export (macos-latest, nightly-latest)	1m 8s
Config export (windows-latest, linked)	4m 35s
Config export (ubuntu-latest, nightly-latest)	1m 5s
Config export (ubuntu-latest, linked)	1m 5s
	15m 49s

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