build: Bump urllib3 from 1.26.8 to 1.26.19 in /docs (#128)

Bumps [urllib3](https://github.com/urllib3/urllib3) from 1.26.8 to 1.26.19.
- [Release notes](https://github.com/urllib3/urllib3/releases)
- [Changelog](https://github.com/urllib3/urllib3/blob/1.26.19/CHANGES.rst)
- [Commits](urllib3/urllib3@1.26.8...1.26.19)

---
updated-dependencies:
- dependency-name: urllib3
  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]

docs/requirements.txt

@@ -93,7 +93,7 @@ tomli==2.0.0
     # via pep517
 tornado==6.4.1
     # via livereload
-urllib3==1.26.8
+urllib3==1.26.19
     # via requests
 wheel==0.38.1
     # via pip-tools