chore(deps): bump python-json-logger in /server/ai-gateway

Bumps [python-json-logger](https://github.com/nhairs/python-json-logger) from 3.3.0 to 4.2.0.
- [Release notes](https://github.com/nhairs/python-json-logger/releases)
- [Changelog](https://github.com/nhairs/python-json-logger/blob/main/docs/changelog.md)
- [Commits](nhairs/python-json-logger@v3.3.0...v4.2.0)

---
updated-dependencies:
- dependency-name: python-json-logger
  dependency-version: 4.2.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

server/ai-gateway/requirements.txt

@@ -11,6 +11,6 @@ redis==8.0.1
 python-jose[cryptography]==3.5.0
 httpx==0.28.1
 python-dotenv==1.2.2
-python-json-logger==3.3.0
+python-json-logger==4.2.0
 google-genai>=1.0.0
 python-multipart==0.0.32