Bump urllib3 from 1.26.8 to 1.26.18

Bumps [urllib3](https://github.com/urllib3/urllib3) from 1.26.8 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@1.26.8...1.26.18)

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

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

requirements.txt

@@ -20,5 +20,5 @@ requests==2.31.0
     #   requests-toolbelt
 requests-toolbelt==0.9.1
     # via pyclowder (setup.py)
-urllib3==1.26.8
+urllib3==1.26.18
     # via requests