ci: update watch dependencies workflow to function again

Author: consideRatio

.github/workflows/watch-dependencies.yaml

@@ -130,14 +130,14 @@ jobs:
   update-jupyterhub-dependencies:
     # Don't run this job on forks
     if: github.repository == 'jupyterhub/zero-to-jupyterhub-k8s'
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
     environment: watch-dependencies
 
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5
         with:
-          python-version: "3.11"
+          python-version: "3.13"
 
       - name: Install Python dependencies
         run: pip install packaging requests