Use activity type in pull_request_review trigger

- Move 'submitted' from if condition to trigger types
- Cleaner and more idiomatic GitHub Actions syntax
- Simplifies the if condition by removing redundant action check

Co-authored-by: thomasturrell <1552612+thomasturrell@users.noreply.github.com>

Author: Copilot

.github/workflows/dependabot-auto-merge.yml

@@ -1,6 +1,8 @@
 name: Dependabot Auto-Merge
 
-on: pull_request_review
+on:
+  pull_request_review:
+    types: [submitted]
 
 permissions:
   contents: write
@@ -9,7 +11,7 @@ permissions:
 jobs:
   auto-merge:
     runs-on: ubuntu-latest
-    if: github.event.action == 'submitted' && github.event.review.state == 'approved' && github.event.pull_request.user.login == 'dependabot[bot]'
+    if: github.event.review.state == 'approved' && github.event.pull_request.user.login == 'dependabot[bot]'
     steps:
       - name: Get Dependabot metadata
         id: metadata