fix a typo in flax T5 attention - attention_mask variable is misnamed

[giganttheo]

What does this PR do?

Fixes a typo in the Flax code for T5 model.

There is a typo in the Attention module of the Flax version of T5, where the attention_mask updated by the _concatenate_to_cache method should override the previous attention_mask but does not because of a misnamed variable.

Fixes #26564

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).

Who can review?

@sanchit-gandhi

[sanchit-gandhi]

Very nice @giganttheo! Thanks for identifying the bug and proposing the fix 🤗 Confirming that the slow tests pass following the fix? As per #26564 (comment) If so, then this all LGTM!

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint.

[giganttheo]

Very nice @giganttheo! Thanks for identifying the bug and proposing the fix 🤗 Confirming that the slow tests pass following the fix? As per #26564 (comment) If so, then this all LGTM!

The slow tests are passing for t5 and longt5:

RUN_SLOW=1 pytest -sv tests/models/t5/test_modeling_flax_t5.py::FlaxT5ModelIntegrationTests

outputs: ================== 6 passed, 4 warnings in 331.38s (0:05:31) ===================

and for the longT5 version:

RUN_SLOW=1 pytest -sv tests/models/longt5/test_modeling_flax_longt5.py::FlaxLongT5ModelIntegrationTests

outputs: =================== 1 passed, 1 warning in 401.61s (0:06:41) ===================

[sanchit-gandhi]

Awesome - thanks for confirming! Requesting a final review from @ArthurZucker

[ArthurZucker]

LGTM! Thanks for catching 🤗