MAINT: Bump ansys-sphinx-theme from 1.6.1 to 1.6.3

Bumps [ansys-sphinx-theme](https://github.com/ansys/ansys-sphinx-theme) from 1.6.1 to 1.6.3.
- [Release notes](https://github.com/ansys/ansys-sphinx-theme/releases)
- [Commits](ansys/ansys-sphinx-theme@v1.6.1...v1.6.3)

---
updated-dependencies:
- dependency-name: ansys-sphinx-theme
  dependency-version: 1.6.3
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

pyproject.toml

@@ -38,7 +38,7 @@ tests = [
     "pytest-cov==6.2.1",
 ]
 doc = [
-    "ansys-sphinx-theme==1.6.1",
+    "ansys-sphinx-theme==1.6.3",
     "jupyter_sphinx==0.5.3",
     "matplotlib==3.10.6",
     "numpydoc==1.9.0",