Update supported GitHub Enterprise Server versions #617

Job	Run time
Upload debug artifacts after failure in analyze (stable-v2.20.3)	3m 7s
Upload debug artifacts after failure in analyze (default)	2m 37s
Upload debug artifacts after failure in analyze (nightly-latest)	2m 18s
Upload debug artifacts after failure in analyze (linked)	2m 25s
Download and check debug artifacts after failure in analyze	9s
	10m 36s

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