⬆️ Update sphinx-immaterial requirement

Updates the requirements on [sphinx-immaterial](https://github.com/jbms/sphinx-immaterial) to permit the latest version.
- [Release notes](https://github.com/jbms/sphinx-immaterial/releases)
- [Commits](jbms/sphinx-immaterial@v0.11.11...v0.12.2)

---
updated-dependencies:
- dependency-name: sphinx-immaterial
  dependency-type: direct:production
...

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

pyproject.toml

@@ -48,7 +48,7 @@ theme-furo = ["furo~=2024.5.4"]
 theme-pydata = ["pydata-sphinx-theme~=0.15.2"]
 theme-rtd = ["sphinx-rtd-theme~=2.0"]
 theme-sbt = ["sphinx-book-theme~=1.1"]
-theme-im = ["sphinx-immaterial~=0.11.11"]
+theme-im = ["sphinx-immaterial>=0.11.11,<0.13.0"]
 
 [tool.flit.sdist]
 exclude = [