ci: bring back the fork check for PRs

Author: skirtles-code

.github/workflows/test.yml

@@ -28,7 +28,7 @@ jobs:
       - name: 'BrowserStack Env Setup'
         uses: 'browserstack/github-actions/setup-env@master'
         # forks do not have access to secrets so just skip this
-        if: github.repository == 'vuejs/router'
+        if: ${{ github.repository == 'vuejs/router' && !github.event.pull_request.head.repo.fork }}
         with:
           username: ${{ secrets.BROWSERSTACK_USERNAME }}
           access-key: ${{ secrets.BROWSERSTACK_ACCESS_KEY }}