Bump ansys-sphinx-theme from 0.9.8 to 0.9.9 in /requirements (#253)

Bumps [ansys-sphinx-theme](https://github.com/ansys/ansys-sphinx-theme) from 0.9.8 to 0.9.9.
- [Release notes](https://github.com/ansys/ansys-sphinx-theme/releases)
- [Commits](ansys/ansys-sphinx-theme@v0.9.8...v0.9.9)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Alex Kaszynski <[email protected]>
Co-authored-by: Roberto Pastor Muela <[email protected]>

requirements/requirements_docs.txt

@@ -1,5 +1,5 @@
 Sphinx<8
-ansys-sphinx-theme==0.9.8
+ansys-sphinx-theme==0.9.9
 imageio==2.30.0
 notfound==1.0.2
 pypandoc==1.11