Fix permissions for `Update schedule.yaml` job

This fixes the permissions required for the job.

Signed-off-by: Sascha Grunert <sgrunert@redhat.com>

.github/workflows/update-schedule.yml

@@ -6,6 +6,9 @@ on:
 jobs:
   create-pull-request:
     name: Create PR (if required)
+    permissions:
+      contents: write
+      pull-requests: write
     if: github.repository == 'kubernetes/website'
     runs-on: ubuntu-latest
     steps: