Bug fix in PR assignee workflow

.github/workflows/add-reviewer-pr.yml

@@ -17,4 +17,4 @@ jobs:
         
     - name: Add Assignee
       run: |
-        curl -X POST -H "Accept: application/vnd.github+json" -H "Authorization: Bearer ${{ secrets.GITHUB_TOKEN}}" https://api.github.com/repos/${{github.repository}}/issues/${{ github.event.issue.number}}/assignees -d '{"assignees":["${{steps.oncall.outputs.CURRENT}}"]}'    
+        curl -X POST -H "Accept: application/vnd.github+json" -H "Authorization: Bearer ${{ secrets.GITHUB_TOKEN}}" https://api.github.com/repos/${{github.repository}}/issues/${{ github.event.pull_request.number}}/assignees -d '{"assignees":["${{steps.oncall.outputs.CURRENT}}"]}'