Add condition to preview to run only on success

The preview workflow doesn't run on success but on completion of the workflow before it. This change ensures that the workflow won't run on a failure or partial success of the PR Release workflow.

.github/workflows/uffizzi-preview.yml

@@ -11,6 +11,7 @@ jobs:
   cache-compose-file:
     name: Cache Compose File
     runs-on: ubuntu-latest
+    if: ${{ github.event.workflow_run.conclusion == 'success' }}
     outputs:
       compose-file-cache-key: ${{ env.COMPOSE_FILE_HASH }}
       pr-number: ${{ env.PR_NUMBER }}