Bump urllib3 from 1.10.1 to 2.5.0 in /python-server/guestbook

Bumps [urllib3](https://github.com/urllib3/urllib3) from 1.10.1 to 2.5.0.
- [Release notes](https://github.com/urllib3/urllib3/releases)
- [Changelog](https://github.com/urllib3/urllib3/blob/main/CHANGES.rst)
- [Commits](urllib3/urllib3@1.10.1...2.5.0)

---
updated-dependencies:
- dependency-name: urllib3
  dependency-version: 2.5.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

python-server/guestbook/requirements.txt

@@ -6,7 +6,7 @@ beautifulsoup4==4.3.2
 PyHamcrest==1.8.0
 six==1.9.0
 httplib2
-urllib3==1.10.1
+urllib3==2.5.0
 google-api-python-client>=0
 oauth2client>=1.3
 uritemplate>=0.6