Try to fix a failing workflow. Too many emails with failing if_merged

Author: aristath

.github/workflows/playground-merged.yml

@@ -14,6 +14,8 @@ jobs:
       pull-requests: write
       actions: read
     steps:
+      - uses: actions/checkout@v4
+
       - name: Prepare blueprint with artifact link
         id: blueprint
         run: |