fix: bump keras from 3.8.0 to 3.9.0

Bumps [keras](https://github.com/keras-team/keras) from 3.8.0 to 3.9.0.
- [Release notes](https://github.com/keras-team/keras/releases)
- [Commits](keras-team/keras@v3.8.0...v3.9.0)

---
updated-dependencies:
- dependency-name: keras
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

requirements.txt

@@ -17,7 +17,7 @@ scikit-learn==1.6.1
 
 # Machine Learning Libraries:
 tensorflow==2.18.0
-keras==3.8.0
+keras==3.9.0
 
 # Natural Language Processing Libraries:
 nltk==3.9.1