Bump jupyter-server in /ai/gen-ai-agents/custom-rag-agent/files

Bumps [jupyter-server](https://github.com/jupyter-server/jupyter_server) from 2.15.0 to 2.18.0.
- [Release notes](https://github.com/jupyter-server/jupyter_server/releases)
- [Changelog](https://github.com/jupyter-server/jupyter_server/blob/main/CHANGELOG.md)
- [Commits](jupyter-server/jupyter_server@v2.15.0...v2.18.0)

---
updated-dependencies:
- dependency-name: jupyter-server
  dependency-version: 2.18.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

ai/gen-ai-agents/custom-rag-agent/files/requirements.txt

@@ -78,7 +78,7 @@ jupyter-events==0.12.0
 jupyter-lsp==2.2.5
 jupyter_client==8.6.3
 jupyter_core==5.7.2
-jupyter_server==2.15.0
+jupyter_server==2.18.0
 jupyter_server_terminals==0.5.3
 jupyterlab==4.4.8
 jupyterlab_pygments==0.3.0