Bump sphinx-immaterial from 0.12.6 to 0.13.9

Bumps [sphinx-immaterial](https://github.com/jbms/sphinx-immaterial) from 0.12.6 to 0.13.9.
- [Release notes](https://github.com/jbms/sphinx-immaterial/releases)
- [Commits](jbms/sphinx-immaterial@v0.12.6...v0.13.9)

---
updated-dependencies:
- dependency-name: sphinx-immaterial
  dependency-version: 0.13.9
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

poetry.lock

@@ -101,7 +101,7 @@ tbump = "^6.11.0"
 
 [tool.poetry.group.docs.dependencies]
 sphinx = ">=5.3,<8.0"
-sphinx-immaterial = ">=0.11,<0.13"
+sphinx-immaterial = ">=0.11,<0.14"
 
 [tool.pytest.ini_options]
 addopts = """