py3: replace mention of “xrange” in docstring by “range”

mercurial/smartset.py

@@ -992,7 +992,7 b' class _spanset(abstractsmartset):'
     """Duck type for baseset class which represents a range of revisions and
     can work lazily and without having all the range in memory
 
-    Note that spanset(x, y) behave almost like xrange(x, y) except for two
+    Note that spanset(x, y) behave almost like range(x, y) except for two
     notable points:
     - when x < y it will be automatically descending,
     - revision filtered with this repoview will be skipped.