Update supported GitHub Enterprise Server versions #860

Job	Run time
Upload debug artifacts after failure in analyze (stable-v2.20.3)	1m 54s
Upload debug artifacts after failure in analyze (nightly-latest)	2m 57s
Upload debug artifacts after failure in analyze (linked)	3m 38s
Upload debug artifacts after failure in analyze (default)	3m 20s
Download and check debug artifacts after failure in analyze	13s
	12m 2s

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