removed note about isolated vertices

In light of Emmanuel's comments on mailing list, this note is apparently not required.

Author: nickeubank

igraph/__init__.py

@@ -1018,8 +1018,6 @@ def community_infomap(self, edge_weights=None, vertex_weights=None, trials=10):
         @return: an appropriate L{VertexClustering} object with an extra attribute
           called C{codelength} that stores the code length determined by the
           algorithm.
-        
-        Note graph must not contain isolated vertices. 
 
         @newfield ref: Reference
         @ref: M. Rosvall and C. T. Bergstrom: Maps of information flow reveal