Bump keras from 3.6.0 to 3.12.0 in /tfx/tools/docker

Bumps [keras](https://github.com/keras-team/keras) from 3.6.0 to 3.12.0.
- [Release notes](https://github.com/keras-team/keras/releases)
- [Commits](keras-team/keras@v3.6.0...v3.12.0)

---
updated-dependencies:
- dependency-name: keras
  dependency-version: 3.12.0
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

tfx/tools/docker/requirements.txt

@@ -158,7 +158,7 @@ jupyterlab_pygments==0.3.0
 jupyterlab_server==2.27.3
 jupyterlab_widgets==1.1.10
 tf-keras==2.16.0
-keras==3.6.0
+keras==3.12.0
 keras-tuner==1.4.7
 kfp==2.5.0
 kfp-pipeline-spec==0.2.2