Get 403 errors when pushing from dependabot

Signed-off-by: John Gomersall <[email protected]>

.github/workflows/container-build.yml

@@ -53,7 +53,7 @@ jobs:
         uses: docker/build-push-action@v6
         with:
           context: .
-          push: true
+          push: ${{ github.event_name != 'pull_request' }}
           file: Dockerfile
           cache-from: type=registry,ref=ghcr.io/${{ github.repository }}:buildcache
           cache-to: type=registry,ref=ghcr.io/${{ github.repository }}:buildcache,mode=max