Fix qwen moe Load balancing loss calculation outside training

[diegoakel]

What does this PR do?

Removes the calculation of load balancing loss for Qwen MoE models when outside training mode.

Fixes #42100

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• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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• Did you write any new necessary tests?

Who can review?

@Rocketknight1

[github-actions]

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

run-slow: qwen3_moe, qwen3_omni_moe, qwen3_vl_moe

[Rocketknight1]

Posted in #42100 as well, but do you know how output_router_logits is getting set? This should only happen when that's set to True.