Move check to job level

(cherry picked from commit 898f039)

Author: jaapio

.github/workflows/backport.yaml

@@ -8,10 +8,10 @@ jobs:
   backport:
     name: "Backport PR"
     runs-on: "ubuntu-latest"
+    if: "${{ github.event.pull_request.merged == true }}"
     steps:
       - name: "Backport Action"
         uses: "sorenlouv/backport-github-action@v9.3.1"
-        if: "${{ github.event.pull_request.merged == true }}"
         with:
           github_token: "${{ secrets.GITHUB_TOKEN }}"
           auto_backport_label_prefix: "auto-backport-to-"