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

Updates the requirements on [python-json-logger](https://github.com/nhairs/python-json-logger) to permit the latest version.
- [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@v2.0.0...v4.1.0)

---
updated-dependencies:
- dependency-name: python-json-logger
  dependency-version: 4.1.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

server/ai-gateway/requirements.txt

@@ -7,6 +7,6 @@ redis>=5.0.0
 python-jose[cryptography]>=3.3.0
 httpx>=0.27.0
 python-dotenv>=1.0.0
-python-json-logger>=2.0.0,<4.0.0
+python-json-logger>=4.1.0,<5.0.0
 google-genai>=1.0.0
 python-multipart>=0.0.7