Revert pull_request_target changes

.github/workflows/mend_ruby.yml

@@ -37,23 +37,11 @@ jobs:
             exit 1
           fi
 
-      # If we are on a PR, checkout the PR head sha, else checkout the default branch
-      - name: "Set the checkout ref"
-        if: success()
-        id: set_ref
-        run: |
-          if [[ "${{ github.event_name }}" == "pull_request_target" ]]; then
-            echo "ref=${{ github.event.pull_request.head.sha }}" >> $GITHUB_OUTPUT
-          else
-            echo "ref=${{ github.ref }}" >> $GITHUB_OUTPUT
-          fi
-
       - name: "checkout"
         if: success()
         uses: "actions/checkout@v4"
         with:
           fetch-depth: 1
-          ref: ${{ steps.set_ref.outputs.ref }}
 
       - name: "setup ruby"
         if: success()