Remove unnecessary object from class definitions

In Python 3, all classes are new-style classes. The object in the
definition is redundant and unnecessary.

doc/usage/extensions/example_numpy.py

@@ -223,7 +223,7 @@ class ExampleError(Exception):
         self.code = code
 
 
-class ExampleClass(object):
+class ExampleClass:
     """The summary line for a class docstring should fit on one line.
 
     If the class has public attributes, they may be documented here