Bump urllib3 in /mpcontribs-serverless/dependencies (#1661)

Bumps [urllib3](https://github.com/urllib3/urllib3) from 1.26.12 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@1.26.12...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>
Co-authored-by: Patrick Huck <phuck@lbl.gov>

mpcontribs-serverless/dependencies/requirements.txt

@@ -265,7 +265,7 @@ ujson==5.5.0
     # via mpcontribs-client
 uncertainties==3.1.7
     # via pymatgen
-urllib3==1.26.12
+urllib3==1.26.18
     # via requests
 wcwidth==0.2.5
     # via prompt-toolkit