fix: ensure correct commit is used in e2e action

- Updated checkout step to use PR head SHA when available
- Prevented issues with incorrect commit being checked out in pull
  request workflows
- Improved workflow reliability for both PR and direct push triggers

Author: chmouel

.github/workflows/e2e.yaml

@@ -62,6 +62,9 @@ jobs:
       TEST_BITBUCKET_SERVER_E2E_REPOSITORY: PAC/pac-e2e-tests
     steps:
       - uses: actions/checkout@v4
+        with:
+          ref: ${{ github.event.pull_request.head.sha || github.sha }}
+
       - uses: actions/setup-go@v5
         with:
           go-version-file: "go.mod"