Need to use pull_request_target to ensure backports workflow runs using the 'target' workflows rather than the workflow in the PR (#2461)

Author: tremble

.github/workflows/backports.yml

@@ -6,7 +6,7 @@ concurrency:
   cancel-in-progress: true
 
 on:
-  pull_request:
+  pull_request_target:
     types:
       - labeled
       - opened