Bump urllib3 in /doc in the pip group across 1 directory

Bumps the pip group with 1 update in the /doc directory: [urllib3](https://github.com/urllib3/urllib3).


Updates `urllib3` from 1.26.4 to 1.26.19
- [Release notes](https://github.com/urllib3/urllib3/releases)
- [Changelog](https://github.com/urllib3/urllib3/blob/main/CHANGES.rst)
- [Commits](urllib3/urllib3@1.26.4...1.26.19)

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

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

doc/requirements.txt

@@ -32,4 +32,4 @@ sphinxcontrib-htmlhelp==2.0.1
 sphinxcontrib-jsmath==1.0.1
 sphinxcontrib-qthelp==1.0.3
 sphinxcontrib-serializinghtml==1.1.5
-urllib3==1.26.4
+urllib3==1.26.19