Use a better test name; remove unnecessary mock side_effect.

Author: mdickinson

ipykernel/tests/test_heartbeat.py

@@ -21,10 +21,9 @@ def test_port_bind_failure_raises():
         assert mock_try_bind.call_count == 1
 
 
-def test_port_bind_failure_succeeds():
+def test_port_bind_success():
     heart = Heartbeat(None)
     with patch.object(heart, '_try_bind_socket') as mock_try_bind:
-        mock_try_bind.side_effect = lambda: None
         heart._bind_socket()
         assert mock_try_bind.call_count == 1