fix: update checkout step to use workflow run head SHA in test

Author: kneerose

.github/workflows/test_backend.yml

@@ -46,6 +46,8 @@ jobs:
     steps:
       - name: Checkout code
         uses: actions/checkout@v4
+        with:
+          ref: ${{ github.event.workflow_run.head_sha }}
 
       - name: Set pending commit status
         id: set-pending-status

.github/workflows/test_integration_playwright.yml

@@ -48,6 +48,8 @@ jobs:
         working-directory: tests/govtool-frontend/playwright
     steps:
       - uses: actions/checkout@v4
+        with:
+            ref: ${{ github.event.workflow_run.head_sha }}
       - name: Set pending commit status
         id: set-pending-status
         run: |