Update review-requested-slack-notification.yml

Use a Set message step

.github/workflows/review-requested-slack-notification.yml

@@ -22,12 +22,16 @@ jobs:
   requested:
     runs-on: ubuntu-latest
     steps:
+      - name: Set message
+        id: set_message
+        run: echo "message=$(echo "👉 ${{ github.event.sender.login }} requested your review in: ${{ github.event.pull_request.title }}" | jq -R .)" >> $GITHUB_OUTPUT
+
       - name: Notify of review request
         uses: slackapi/[email protected]
         with:
           payload: |
             {
-              "message": ${{toJSON("👉 ${{github.event.sender.login}} requested your review in: ${{github.event.pull_request.title}}")}}, 
+              "message": ${{ steps.set_message.outputs.message }}
               "user": "${{ secrets[format('slack_email_{0}', github.event.requested_reviewer.login)] }}",
               "pr_url": "${{ github.event.pull_request.html_url }}"
             }