Add warning about 3.0 #9435

Job	Run time
GraphQL (pinned) (3.10, ubuntu-22.04)	2m 38s
GraphQL (pinned) (3.11, ubuntu-22.04)	2m 5s
GraphQL (pinned) (3.9, ubuntu-22.04)	2m 59s
GraphQL (pinned) (3.8, ubuntu-22.04)	2m 25s
GraphQL (pinned) (3.12, ubuntu-22.04)	3m 33s
GraphQL (pinned) (3.13, ubuntu-22.04)	3m 55s
GraphQL (pinned) (3.7, ubuntu-22.04)	1m 53s
All pinned GraphQL tests passed	4s
	19m 32s

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