Bump urllib3 from 1.25.3 to 1.26.5 in /docs

Bumps [urllib3](https://github.com/urllib3/urllib3) from 1.25.3 to 1.26.5.
- [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/1.25.3...1.26.5)

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

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

docs/requirements.txt

@@ -48,7 +48,7 @@ toml==0.10.0
 tornado==6.0.3
 tqdm==4.32.2
 twine==1.13.0
-urllib3==1.25.3
+urllib3==1.26.5
 watchdog==0.9.0
 wcwidth==0.1.7
 webencodings==0.5.1