Fix workflow

Author: therve

.github/workflows/prepare_release.yml

@@ -18,6 +18,9 @@ jobs:
           app_id: ${{ secrets.PIPELINE_GITHUB_APP_ID }}
           private_key: ${{ secrets.PIPELINE_GITHUB_APP_PRIVATE_KEY }}
 
+      - name: Checkout code
+        uses: actions/checkout@v3
+
       - name: Calculate version
         id: get_version
         run: |