ci: fix dependabot commit detection (#59)

Author: soumyamahunt

.github/workflows/main.yml

@@ -20,7 +20,7 @@ on:
 jobs:
   dependabot:
     name: Check dependabot PR raised updating swiftorg
-    if: github.event_name == 'pull_request' && github.event.pull_request.head.user.login == 'dependabot[bot]'
+    if: github.event_name == 'pull_request' && github.event.sender.login == 'dependabot[bot]'
     runs-on: ubuntu-latest
     concurrency:
       group: dependabot-${{ github.ref }}