Change head-sha in commit (#10196)

Author: sarahchen6

.github/workflows/pin-system-tests.yaml

@@ -40,6 +40,11 @@ jobs:
         uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
         with:
           ref: ${{ steps.define-base-branch.outputs.base_branch }}
+      
+      - name: Get latest commit SHA of base branch
+        id: get-latest-commit-sha
+        run: |
+          echo "sha=$(git rev-parse HEAD)" >> $GITHUB_OUTPUT
 
       - name: Define branch name
         id: define-branch
@@ -87,7 +92,7 @@ jobs:
         with:
           token: "${{ steps.octo-sts.outputs.token }}"
           branch: "${{ steps.define-branch.outputs.branch }}"
-          head-sha: "${{ github.sha }}"
+          head-sha: "${{ steps.get-latest-commit-sha.outputs.sha }}"
           create-branch: true
           command: push
           commits: "${{ steps.create-commit.outputs.commit }}"