Fix event_name

Author: reakaleek

.github/workflows/preview-build.yml

@@ -59,7 +59,7 @@ jobs:
         id: deployment
         env:
           PR_NUMBER: ${{ github.event.pull_request.number }}
-          REF: ${{ github.event_name == 'pull_request' && github.event.pull_request.head.sha || github.ref_name }}
+          REF: ${{ github.event_name == 'pull_request_target' && github.event.pull_request.head.sha || github.ref_name }}
         with:
           result-encoding: string
           script: |