Issue #28221: Remove unused assignment from test_asyncore_server()

The later value of FOO is fine. The test just needs to verify that the server
converted it to lowercase.

Lib/test/test_ssl.py

@@ -2688,8 +2688,6 @@ else:
 
         def test_asyncore_server(self):
             """Check the example asyncore integration."""
-            indata = "TEST MESSAGE of mixed case\n"
-
             if support.verbose:
                 sys.stdout.write("\n")