Update supported GitHub Enterprise Server versions #864

Job	Run time
Upload debug artifacts after failure in analyze (stable-v2.20.3)	2m 1s
Upload debug artifacts after failure in analyze (default)	3m 27s
Upload debug artifacts after failure in analyze (nightly-latest)	3m 25s
Upload debug artifacts after failure in analyze (linked)	3m 29s
Download and check debug artifacts after failure in analyze	23s
	12m 45s

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