Fix testing imports

Author: NoahStapp

test/test_topology.py

@@ -38,7 +38,7 @@
 from pymongo.synchronous.pool import PoolOptions
 from pymongo.synchronous.server import Server
 from pymongo.synchronous.settings import TopologySettings
-from pymongo.synchronous.topology import Topology, _ErrorContext, _filter_servers
+from pymongo.synchronous.topology import Topology, _ErrorContext
 from pymongo.topology_description import TOPOLOGY_TYPE