Add missing double quote

Author: brianhlin

action.yml

@@ -56,7 +56,7 @@ runs:
       docker_repo="$REGISTRY/opensciencegrid/${{ steps.generate-image-name.outputs.image }}"
       tag_list=()
       for image_tag in "$OSG_SERIES-$REPO" "$OSG_SERIES-$REPO-$(date +%Y%m%d-%H%M)"; do
-        tag_list+=($docker_repo":"$image_tag")
+        tag_list+=("$docker_repo":"$image_tag")
       done
       IFS=,
       echo "::set-output name=taglist::${tag_list[*]}"