Remove keepalive workflow as it is no longer allowed

Author: connorjward

.github/workflows/website.yml

@@ -105,18 +105,3 @@ jobs:
     steps:
       - name: Deploy to GitHub Pages
         uses: actions/deploy-pages@v4
-
-  keepalive:
-    name: Keepalive
-    if: github.ref == 'refs/heads/main'
-    runs-on: ubuntu-latest
-    permissions:
-      actions: write
-    steps:
-      - name: Set repo permissions
-        run: |
-          git config --global --add safe.directory /home/runner/work/firedrakeproject.github.io/firedrakeproject.github.io
-      - uses: actions/checkout@v4
-      - uses: gautamkrishnar/keepalive-workflow@v2
-        with:
-          time_elapsed: 30