bpo-46198: Fix test_asyncio.test_sslproto (GH-31801)

GH-30297 removed a duplicate `from test import support` statement from `test_asyncio.test_sslproto`. However, in between that PR being filed and it being merged, GH-31275 removed the _other_ `from test import support` statement. This means that `support` is now undefined in `test_asyncio.test_sslproto`, causing the CI to fail on all platforms for all PRS.

Lib/test/test_asyncio/test_sslproto.py

@@ -4,6 +4,7 @@
 import socket
 import unittest
 import weakref
+from test import support
 from unittest import mock
 try:
     import ssl