only assign XLS numbers after a maintainer's approval

.github/workflows/assign-xls-number.yml

@@ -1,13 +1,15 @@
 name: Assign XLS Number
 
 on:
-  pull_request_target:
-    types: [opened, synchronize, reopened, ready_for_review]
+  pull_request_review:
+    types: [submitted]
 
 jobs:
   assign-xls-number:
     runs-on: ubuntu-latest
     name: Assign XLS Number to Draft
+    # Only run when the review is an approval
+    if: github.event.review.state == 'approved'
     permissions:
       pull-requests: write
       issues: write