Update supported GitHub Enterprise Server versions #863

Job	Run time
Upload debug artifacts after failure in analyze (stable-v2.20.3)	1m 49s
Upload debug artifacts after failure in analyze (default)	3m 14s
Upload debug artifacts after failure in analyze (nightly-latest)	3m 1s
Upload debug artifacts after failure in analyze (linked)	2m 54s
Download and check debug artifacts after failure in analyze	10s
	11m 8s

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