fix ResourceWarnings of test_kill_issue43884 in asyncio (#154178)

Author: kumaraditya303

Lib/test/test_asyncio/test_subprocess.py

@@ -220,7 +220,7 @@ def test_kill_issue43884(self):
             # kills the process and all its children.
             creationflags = CREATE_NEW_PROCESS_GROUP
         proc = self.loop.run_until_complete(
-            asyncio.create_subprocess_shell(blocking_shell_command, stdout=asyncio.subprocess.PIPE,
+            asyncio.create_subprocess_shell(blocking_shell_command,
             creationflags=creationflags)
         )
         self.loop.run_until_complete(asyncio.sleep(1))