Update supported GitHub Enterprise Server versions #4415

Job	Run time
Diagnostic export (ubuntu-latest, linked)	1m 4s
Diagnostic export (windows-latest, linked)	2m 37s
Diagnostic export (ubuntu-latest, nightly-latest)	1m 10s
Diagnostic export (windows-latest, nightly-latest)	2m 50s
Diagnostic export (macos-latest, linked)	1m 32s
Diagnostic export (macos-latest, nightly-latest)	1m 19s
	10m 32s

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