Bump urllib3 from 1.26.17 to 1.26.18 in /docs/.sphinx (#303)

Bumps [urllib3](https://github.com/urllib3/urllib3) from 1.26.17 to 1.26.18.
- [Release notes](https://github.com/urllib3/urllib3/releases)
- [Changelog](https://github.com/urllib3/urllib3/blob/main/CHANGES.rst)
- [Commits](urllib3/urllib3@1.26.17...1.26.18)

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

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

docs/.sphinx/requirements.txt

@@ -155,7 +155,7 @@ tqdm==4.65.0
     # via mpire
 typing-extensions==4.5.0
     # via pydata-sphinx-theme
-urllib3==1.26.17
+urllib3==1.26.18
     # via requests
 wrapt==1.15.0
     # via deprecated