Update prompts.py

IPython/core/prompts.py

@@ -19,8 +19,5 b' class LazyEvaluate(object):'
     def __str__(self):
         return str(self())
 
-    def __unicode__(self):
-        return self.__str__()
-
     def __format__(self, format_spec):
         return format(self(), format_spec)