maint: bump ansys-sphinx-theme from 1.2.4 to 1.2.6

Bumps [ansys-sphinx-theme](https://github.com/ansys/ansys-sphinx-theme) from 1.2.4 to 1.2.6.
- [Release notes](https://github.com/ansys/ansys-sphinx-theme/releases)
- [Commits](ansys/ansys-sphinx-theme@v1.2.4...v1.2.6)

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

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

requirements/requirements_doc.txt

@@ -1,4 +1,4 @@
-ansys-sphinx-theme==1.2.4
+ansys-sphinx-theme==1.2.6
 jupyterlab==4.3.1
 jupytext==1.16.6
 jupyter-server==2.15.0