Splitting and only retaining timestamp for frontend tag artifact

Without this current internal script would fail since it would prefix branch name internally as well.
Once internal script has been updated, will remove artifacts completely.

.github/workflows/image_build_push.yml

@@ -97,7 +97,7 @@ jobs:
         if [ "${{ github.event_name }}" == "push" ]; then
           echo ${{ steps.date.outputs.date }} > frontend_tag_file.txt
         else
-          echo ${{ steps.set-tags.outputs.PUBLIC_DASH_FRONTEND_IMAGE_TAG }} > frontend_tag_file.txt
+          echo ${{ steps.set-tags.outputs.PUBLIC_DASH_FRONTEND_IMAGE_TAG }} | cut -d'_' -f2 > frontend_tag_file.txt
         fi
         echo ${{ steps.date.outputs.date }} > notebook_tag_file.txt
         echo "Created tag text files"