chore(deps): update redis requirement in /server/ai-gateway

Updates the requirements on [redis](https://github.com/redis/redis-py) to permit the latest version.
- [Release notes](https://github.com/redis/redis-py/releases)
- [Changelog](https://github.com/redis/redis-py/blob/master/CHANGES)
- [Commits](redis/redis-py@v5.0.0...v8.1.0)

---
updated-dependencies:
- dependency-name: redis
  dependency-version: 8.1.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

server/ai-gateway/requirements.txt

@@ -3,7 +3,7 @@ uvicorn[standard]>=0.30.0
 gunicorn>=22.0.0
 openai>=1.50.0
 pydantic>=2.0.0
-redis>=5.0.0
+redis>=8.1.0
 python-jose[cryptography]>=3.3.0
 httpx>=0.27.0
 python-dotenv>=1.0.0