chore(deps): bump keras from 3.0.5 to 3.9.0 in /dataflow/gemma

Bumps [keras](https://github.com/keras-team/keras) from 3.0.5 to 3.9.0.
- [Release notes](https://github.com/keras-team/keras/releases)
- [Commits](keras-team/keras@v3.0.5...v3.9.0)

---
updated-dependencies:
- dependency-name: keras
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

dataflow/gemma/requirements.txt

@@ -1,4 +1,4 @@
 apache_beam[gcp]==2.54.0
 protobuf==4.25.0
 keras_nlp==0.8.2
-keras==3.0.5
+keras==3.9.0