bpo-30354: Update data model documentation for super() (GH-1561)

The data model section of the language reference was written well
before the zero-argument form of super() was added.

To avoid giving the impression that they're doing something
unusual, this updates the description of `__new__` and `__init__`
to use the zero-argument form.

Patch by Cheryl Sabella.

Doc/reference/datamodel.rst

@@ -1119,9 +1119,9 @@ Basic customization
    (usually an instance of *cls*).
 
    Typical implementations create a new instance of the class by invoking the
-   superclass's :meth:`__new__` method using ``super(currentclass,
-   cls).__new__(cls[, ...])`` with appropriate arguments and then modifying the
-   newly-created instance as necessary before returning it.
+   superclass's :meth:`__new__` method using ``super().__new__(cls[, ...])``
+   with appropriate arguments and then modifying the newly-created instance
+   as necessary before returning it.
 
    If :meth:`__new__` returns an instance of *cls*, then the new instance's
    :meth:`__init__` method will be invoked like ``__init__(self[, ...])``, where
@@ -1145,7 +1145,7 @@ Basic customization
    class constructor expression.  If a base class has an :meth:`__init__`
    method, the derived class's :meth:`__init__` method, if any, must explicitly
    call it to ensure proper initialization of the base class part of the
-   instance; for example: ``BaseClass.__init__(self, [args...])``.
+   instance; for example: ``super().__init__([args...])``.
 
    Because :meth:`__new__` and :meth:`__init__` work together in constructing
    objects (:meth:`__new__` to create it, and :meth:`__init__` to customize it),
@@ -1582,8 +1582,8 @@ Class Binding
    ``A.__dict__['x'].__get__(None, A)``.
 
 Super Binding
-   If ``a`` is an instance of :class:`super`, then the binding ``super(B,
-   obj).m()`` searches ``obj.__class__.__mro__`` for the base class ``A``
+   If ``a`` is an instance of :class:`super`, then the binding ``super(B, obj).m()``
+   searches ``obj.__class__.__mro__`` for the base class ``A``
    immediately preceding ``B`` and then invokes the descriptor with the call:
    ``A.__dict__['m'].__get__(obj, obj.__class__)``.