fix kullback_leibler doc

gensim/matutils.py

@@ -446,7 +446,7 @@ def isbow(vec):
 def kullback_leibler(vec1, vec2, num_features=None):
     """
     A distance metric between two probability distributions.
-    Returns a distance value in range <0,1> where values closer to 0 mean less distance (and a higher similarity)
+    Returns a distance value in range <0,+∞> where values closer to 0 mean less distance (and a higher similarity)
     Uses the scipy.stats.entropy method to identify kullback_leibler convergence value.
     If the distribution draws from a certain number of docs, that value must be passed.
     """