Update downstream.yml

Author: blink1073

.github/workflows/downstream.yml

@@ -43,7 +43,7 @@ jobs:
         if: ${{ always() }}
         run: pytest --pyargs jupyter_client
       - name: Test jupyter_kernel_test
-        run:
+        run: |
           git clone [email protected]:jupyter/jupyter_kernel_test.git
           cd jupyter_kernel_test
           pip install -e ".[test]"