fix: don't push image when skip_unchanged_digest is set

Kaniko default behavior changed, `--tarPath` alone is not enough to skip the push to registery, `--no-push` is now required as well.

Reference:
GoogleContainerTools/kaniko#1503

entrypoint.sh

@@ -61,7 +61,7 @@ export DOCKERFILE="--dockerfile $CONTEXT_PATH/${INPUT_BUILD_FILE:-Dockerfile}"
 export TARGET=${INPUT_TARGET:+"--target=$INPUT_TARGET"}
 
 if [ ! -z $INPUT_SKIP_UNCHANGED_DIGEST ]; then
-    export DESTINATION="--digest-file digest --tarPath image.tar --destination $IMAGE"
+    export DESTINATION="--digest-file digest --no-push --tarPath image.tar --destination $IMAGE"
 else
     export DESTINATION="--destination $IMAGE"
     if [ ! -z $IMAGE_LATEST ]; then