remove is_smooth from max

Author: Transurgeon

cvxpy/atoms/max.py

@@ -114,10 +114,6 @@ def is_atom_log_log_concave(self) -> bool:
         """
         return False
 
-    def is_smooth(self):
-        """max is not a smooth function of its args"""
-        return False
-    
     def is_incr(self, idx) -> bool:
         """Is the composition non-decreasing in argument idx?
         """