[size-report] fix the source code

Author: bukepo

.github/workflows/size.yml

@@ -53,6 +53,11 @@ jobs:
         egress-policy: audit # TODO: change to 'egress-policy: block' after couple of runs
 
     - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+    - name: Checkout Pull Request
+      if: ${{ github.event_name == 'pull_request_target' }}
+      run: |
+        git fetch origin pull/${{ github.event.pull_request.number }}/head
+        git checkout FETCH_HEAD
     - name: Run
       env:
         GITHUB_TOKEN: "${{ secrets.GITHUB_TOKEN }}"