Bump urllib3 from 2.5.0 to 2.6.0 in /doc (#899)

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](urllib3/urllib3@2.5.0...2.6.0)

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

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

Author: dependabot[bot]

doc/requirements.txt

@@ -80,5 +80,5 @@ sphinxcontrib-qthelp==2.0.0
     # via sphinx
 sphinxcontrib-serializinghtml==2.0.0
     # via sphinx
-urllib3==2.5.0
+urllib3==2.6.0
     # via requests