chore(topology/list): one import per line (#4479)

This one seems to have slipped through previous efforts

src/topology/list.lean

@@ -5,7 +5,8 @@ Authors: Johannes Hölzl
 
 Topology on lists and vectors.
 -/
-import topology.constructions topology.algebra.group
+import topology.constructions
+import topology.algebra.group
 
 open topological_space set filter
 open_locale topological_space filter