Update mkdocstrings[python-legacy] requirement from ~=0.25.2 to ~=0.26.1

Updates the requirements on [mkdocstrings[python-legacy]](https://github.com/mkdocstrings/mkdocstrings) to permit the latest version.
- [Release notes](https://github.com/mkdocstrings/mkdocstrings/releases)
- [Changelog](https://github.com/mkdocstrings/mkdocstrings/blob/main/CHANGELOG.md)
- [Commits](mkdocstrings/mkdocstrings@0.25.2...0.26.1)

---
updated-dependencies:
- dependency-name: mkdocstrings[python-legacy]
  dependency-type: direct:production
...

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

requirements_docs.txt

@@ -4,5 +4,5 @@ mkdocs~=1.6; python_version>="3.8"
 mkdocs-awesome-pages-plugin~=2.9
 mkdocs-material~=9.5; python_version>="3.8"
 mkdocs-material~=9.2; python_version<"3.8"
-mkdocstrings[python-legacy]~=0.25.2; python_version>="3.8"
+mkdocstrings[python-legacy]~=0.26.1; python_version>="3.8"
 mkdocstrings[python-legacy]~=0.22.0; python_version<"3.8"