[Main]fix main CI no space problem

Signed-off-by: Lyndon-Li <lyonghui@vmware.com>

.github/workflows/push.yml

@@ -99,4 +99,7 @@ jobs:
     - name: Publish container image to GCR
       if: github.repository == 'vmware-tanzu/velero'
       run: |
+        sudo swapoff -a
+        sudo rm -f /mnt/swapfile
+        docker image prune -a --force
         REGISTRY=gcr.io/velero-gcp ./hack/docker-push.sh