Bump sphinx-immaterial from 0.11.7 to 0.11.8

Bumps [sphinx-immaterial](https://github.com/jbms/sphinx-immaterial) from 0.11.7 to 0.11.8.
- [Release notes](https://github.com/jbms/sphinx-immaterial/releases)
- [Commits](jbms/sphinx-immaterial@v0.11.7...v0.11.8)

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

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Author: dependabot[bot]