Fix typo in StableGraph::edge_indices doc
diff --git a/src/graph_impl/stable_graph/mod.rs b/src/graph_impl/stable_graph/mod.rs
index 7c98681..6abfa99 100644
--- a/src/graph_impl/stable_graph/mod.rs
+++ b/src/graph_impl/stable_graph/mod.rs
@@ -509,7 +509,7 @@
         }
     }
 
-    /// Return an iterator over the node indices of the graph
+    /// Return an iterator over the edge indices of the graph
     pub fn edge_indices(&self) -> EdgeIndices<E, Ix> {
         EdgeIndices {
             iter: enumerate(self.raw_edges()),