Bump keras from 2.2.4 to 2.13.1 in /quickstart/unattended-execution

Bumps [keras](https://github.com/keras-team/keras) from 2.2.4 to 2.13.1.
- [Release notes](https://github.com/keras-team/keras/releases)
- [Commits](keras-team/keras@2.2.4...v2.13.1)

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

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

Author: dependabot[bot]

quickstart/unattended-execution/requirements.txt

@@ -1 +1 @@
-Keras==2.2.4
+Keras==2.13.1