Bump urllib3 from 1.25.9 to 1.26.5 in /doc/.sphinx

Bumps [urllib3](https://github.com/urllib3/urllib3) from 1.25.9 to 1.26.5.
- [Release notes](https://github.com/urllib3/urllib3/releases)
- [Changelog](https://github.com/urllib3/urllib3/blob/main/CHANGES.rst)
- [Commits](urllib3/urllib3@1.25.9...1.26.5)

---
updated-dependencies:
- dependency-name: urllib3
  dependency-type: direct:production
...

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

doc/.sphinx/requirements.txt

@@ -28,4 +28,4 @@ requests==2.24.0
 six==1.15.0
 snowballstemmer==2.0.0
 sphinxcontrib-websupport==1.2.2
-urllib3==1.25.9
+urllib3==1.26.5