Update supported GitHub Enterprise Server versions #546

Job	Run time
Upload debug artifacts after failure in analyze (stable-v2.20.3)	1m 36s
Upload debug artifacts after failure in analyze (linked)	1m 42s
Upload debug artifacts after failure in analyze (nightly-latest)	2m 14s
Upload debug artifacts after failure in analyze (default)	1m 54s
Download and check debug artifacts after failure in analyze	10s
	7m 36s

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