Add warning about 3.0 #9448

Job	Run time
Common (pinned) (3.8, ubuntu-22.04)	5m 51s
Common (pinned) (3.11, ubuntu-22.04)	5m 44s
Common (pinned) (3.12, ubuntu-22.04)	5m 24s
Common (pinned) (3.9, ubuntu-22.04)	7m 13s
Common (pinned) (3.7, ubuntu-22.04)	3m 48s
Common (pinned) (3.13, ubuntu-22.04)	5m 26s
Common (pinned) (3.10, ubuntu-22.04)	5m 47s
All pinned Common tests passed	3s
	39m 16s

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