Update pr workflow #5

Author: BirjuVachhani

.github/workflows/pr.yml

@@ -12,7 +12,7 @@ jobs:
     steps:
       - uses: actions/checkout@v3
         with:
-          ref: ${{ 'refs/pull/' + github.event.workflow_run.outputs.pr-number + '/head' }}
+          ref: 'refs/pull/${{ github.event.workflow_run.outputs.pr-number }}/head'
       - name: Install Flutter
         uses: subosito/flutter-action@v2
         with: