Bump urllib3 from 2.6.0 to 2.6.3 in /docs/sphinx (#383)

Bumps [urllib3](https://github.com/urllib3/urllib3) from 2.6.0 to 2.6.3.
- [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/2.6.0...2.6.3)

---
updated-dependencies:
- dependency-name: urllib3
  dependency-version: 2.6.3
  dependency-type: indirect
...

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

docs/sphinx/requirements.txt

@@ -266,7 +266,7 @@ typing-extensions==4.13.2
     #   pygithub
     #   referencing
     #   sqlalchemy
-urllib3==2.6.0
+urllib3==2.6.3
     # via
     #   pygithub
     #   requests