fix(ci): set issue number correctly for closed issue workflow

.github/workflows/closed-issue.yml

@@ -12,7 +12,7 @@ jobs:
       - uses: peter-evans/create-or-update-comment@v4
         with:
           token: ${{ github.token }}
-          issue-number: ${{ github.event.pull_request.number }}
+          issue-number: ${{ github.event.issue.number }}
           body: |
             Closed issues are **NOT** monitored, so commenting here is likely to be not seen.
             If you think this is *still unresolved* and have **more information** to bring, please create another issue.