Bump ray from 2.48.0 to 2.50.0 in /api-server/qna-eval

Bumps [ray](https://github.com/ray-project/ray) from 2.48.0 to 2.50.0.
- [Release notes](https://github.com/ray-project/ray/releases)
- [Commits](ray-project/ray@ray-2.48.0...ray-2.50.0)

---
updated-dependencies:
- dependency-name: ray
  dependency-version: 2.50.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

api-server/qna-eval/requirements.txt

@@ -130,7 +130,7 @@ python-dateutil==2.9.0.post0
 python-dotenv==1.1.1
 PyYAML==6.0.2
 pyzmq==27.0.1
-ray==2.48.0
+ray==2.50.0
 referencing==0.36.2
 regex==2025.7.34
 requests==2.32.4