Bump ansys-sphinx-theme from 0.8.1 to 0.9.6 in /requirements (#1521)

Bumps [ansys-sphinx-theme](https://github.com/ansys/ansys-sphinx-theme) from 0.8.1 to 0.9.6.
- [Release notes](https://github.com/ansys/ansys-sphinx-theme/releases)
- [Commits](ansys/ansys-sphinx-theme@v0.8.1...v0.9.6)

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Jorge Martínez <28702884+jorgepiloto@users.noreply.github.com>

requirements/requirements_doc.txt

@@ -2,7 +2,7 @@ Sphinx==5.3.0
 jupyter_sphinx==0.4.0
 numpydoc==1.5.0
 matplotlib==3.6.3
-ansys-sphinx-theme==0.8.1
+ansys-sphinx-theme==0.9.6
 pypandoc==1.10
 pytest-sphinx==0.5.0
 sphinx-autobuild==2021.3.14