Only download github artifacts for on-host workflows

b/290997541

.github/workflows/unit_test_report.yaml

@@ -19,6 +19,7 @@ jobs:
     name: Upload Unit Test Reports
     steps:
       - name: Download '${{ github.event.workflow_run.name }}' Unit Test Results
+        if: github.event.workflow_run.name == 'evergreen' || github.event.workflow_run.name == 'linux' || github.event.workflow_run.name == 'win32'
         # The `download-artifact` action can only access artifacts that were uploaded in the same workflow.
         # Since it was not this workflow that uploaded the artifacts we must use rest api to download them.
         # https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#using-data-from-the-triggering-workflow