Bump urllib3 from 1.26.5 to 1.26.18

Bumps [urllib3](https://github.com/urllib3/urllib3) from 1.26.5 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@1.26.5...1.26.18)

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

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

requirements.txt

@@ -9,4 +9,4 @@ elasticsearch==2.2.0
 nose==1.3.7
 python-dateutil==2.4.2
 six==1.10.0
-urllib3==1.26.5
+urllib3==1.26.18