Update supported GitHub Enterprise Server versions #3859

Job	Run time
Diagnostic export (ubuntu-latest, linked)	1m 8s
Diagnostic export (macos-latest, linked)	1m 5s
Diagnostic export (ubuntu-latest, nightly-latest)	1m 5s
Diagnostic export (windows-latest, nightly-latest)	3m 51s
Diagnostic export (macos-latest, nightly-latest)	1m 35s
Diagnostic export (windows-latest, linked)	3m 22s
	12m 6s

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