Bump enum-tools[sphinx] from 0.12.0 to 0.13.0 in /requirements (#2227)

Bumps [enum-tools[sphinx]](https://github.com/domdfcoding/enum_tools) from 0.12.0 to 0.13.0.
- [Release notes](https://github.com/domdfcoding/enum_tools/releases)
- [Commits](domdfcoding/enum_tools@v0.12.0...v0.13.0)

---
updated-dependencies:
- dependency-name: enum-tools[sphinx]
  dependency-version: 0.13.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

requirements/requirements_docs.txt

@@ -1,5 +1,5 @@
 ansys-sphinx-theme[autoapi]==1.3.2
-enum-tools[sphinx]==0.12.0
+enum-tools[sphinx]==0.13.0
 graphviz==0.20.1
 imageio==2.37.0
 imageio-ffmpeg==0.6.0