Bump urllib3 from 1.26.2 to 1.26.5 in /docs

Bumps [urllib3](https://github.com/urllib3/urllib3) from 1.26.2 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@1.26.2...1.26.5)

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

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

docs/requirements.txt

@@ -41,5 +41,5 @@ sphinxcontrib-qthelp==1.0.3
 sphinxcontrib-serializinghtml==1.1.4
 typed-ast==1.4.2
 typing-extensions==3.7.4.3 ; python_version < '3.8'
-urllib3==1.26.2
+urllib3==1.26.5
 zipp==3.4.0