removed gemma3 eager warning

[August-murr]

What does this PR do?

Fixes #40723

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[Rocketknight1]

cc @Cyrilvallez to decide if we still need that warning or not

[Cyrilvallez]

Indeed, I wanted to remove it before as well, so happy to do it! It's an artifact of the time when the hybrid attention was very fragile due to the masking etc, but it is no longer the case and there is no need for the warning.

It should be removed in modular though, and in other gemmas as well!

[github-actions]

[For maintainers] Suggested jobs to run (before merge)

run-slow: gemma2, gemma3, gemma3n, t5gemma

[Cyrilvallez]

Perfect, thanks a lot! Happy to remove!