Use TAG env var in publish-funcitons.sh

Author: frankfarzan

go/scripts/publish-functions.sh

@@ -21,7 +21,7 @@ FUNCS=(gatekeeper_validate)
 
 for f in ${FUNCS[@]}; do
     image_name=$(echo $f | sed -e 's/_/-/g')
-    image=gcr.io/kpt-functions/${image_name}:dev
+    image=gcr.io/kpt-functions/${image_name}:${TAG}
     docker_file=/tmp/$image_name.Dockerfile
     sed "s/\$FUNC/$f/g" build/func.Dockerfile > $docker_file
     set -x