Bump ansys-sphinx-theme from 0.9.7 to 0.9.8 in /requirements (#248)

Bumps [ansys-sphinx-theme](https://github.com/ansys/ansys-sphinx-theme) from 0.9.7 to 0.9.8.
- [Release notes](https://github.com/ansys/ansys-sphinx-theme/releases)
- [Commits](ansys/ansys-sphinx-theme@v0.9.7...v0.9.8)

---
updated-dependencies:
- dependency-name: ansys-sphinx-theme
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

requirements/requirements_docs.txt

@@ -1,5 +1,5 @@
 Sphinx<6
-ansys-sphinx-theme==0.9.7
+ansys-sphinx-theme==0.9.8
 notfound==1.0.2
 pypandoc==1.11
 pyvista==0.38.5