fix(scripts): delete temp GCP key before success message

Restore the immediate rm after Secrets Manager store so the status
line is accurate and the key is gone before later steps; EXIT trap
still covers failure paths.

scripts/gcp-setup.sh

@@ -119,6 +119,7 @@ else
     --region "$AWS_REGION"
   echo "Created secret forgejo/gcs-sa-key."
 fi
+rm -f "$KEY_FILE"
 echo "Key stored in AWS Secrets Manager, local copy deleted."
 
 # --- Storage Transfer ---