Bump urllib3 from 2.5.0 to 2.6.0 in /docs/sphinx

Bumps [urllib3](https://github.com/urllib3/urllib3) from 2.5.0 to 2.6.0.
- [Release notes](https://github.com/urllib3/urllib3/releases)
- [Changelog](https://github.com/urllib3/urllib3/blob/main/CHANGES.rst)
- [Commits](https://github.com/urllib3/urllib3/compare/2.5.0...2.6.0)

---
updated-dependencies:
- dependency-name: urllib3
  dependency-version: 2.6.0
  dependency-type: indirect
...

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

docs/sphinx/requirements.txt

@@ -281,7 +281,7 @@ typing-extensions==4.15.0
     #   pygithub
     #   referencing
     #   sqlalchemy
-urllib3==2.5.0
+urllib3==2.6.0
     # via
     #   pygithub
     #   requests