Dont allow underscore in the app tag.

Author: gcg

action.yaml

@@ -52,7 +52,7 @@ runs:
     - name: Get url friendly branch name
       shell: bash
       run: |
-        url=$(sed -E 's#refs/[^\/]*/##;s/[^a-zA-Z0-9_]+/-/g;s/-+/-/g;s/^-*//;s/-*$//' <<<"${GITHUB_HEAD_REF}")
+        url=$(sed -E 's#refs/[^\/]*/##;s/[^a-zA-Z0-9]+/-/g;s/-+/-/g;s/^-*//;s/-*$//' <<<"${GITHUB_HEAD_REF}")
         tolower=${url,,}
         reduce=$(echo $tolower | cut -c -20)
         echo "BRANCH_URL=$(echo ${reduce%-})" >> $GITHUB_ENV