Update keras requirement from ^2.13.1 to ^3.9.1

Updates the requirements on [keras](https://github.com/keras-team/keras) to permit the latest version.
- [Release notes](https://github.com/keras-team/keras/releases)
- [Commits](keras-team/keras@v2.13.1...v3.9.1)

---
updated-dependencies:
- dependency-name: keras
  dependency-version: 3.9.1
  dependency-type: direct:production
...

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

Author: dependabot[bot]

pyproject.toml

@@ -12,7 +12,7 @@ mechanicalsoup = "^1.3.0"
 defusedxml = "^0.7.1"
 pandas = "^2.2.2"
 pdb-tools = "^2.5.0"
-keras = "^2.13.1"
+keras = "^3.9.1"
 tensorflow = "^2.13.0"
 idna = "^3.7"
 requests = "2.31.0"