Fix Windows subprocess handle issue

Author: davidbrochart

tests/services/sessions/test_api.py

@@ -304,4 +304,4 @@ async def test_modify_kernel_id(session_client, fetch):
     assert kernel_list == [kernel]
 
     # Need to find a better solution to this.
-    await session_client.cleanup()
+    await session_client.cleanup()