Use right markup for CPython implementation

Author: furkanonder

Doc/c-api/object.rst

@@ -286,7 +286,7 @@ Object Protocol
    >>> D.__base__
    <class 'B'>
 
-   Note that behavior of the ``__base__`` attribute is dependent on the CPython implementation.
+   Note that behavior of the ``__base__`` attribute is dependent on the :term:`CPython` implementation.
 
 .. c:function:: int PyObject_IsInstance(PyObject *inst, PyObject *cls)
 

Doc/library/stdtypes.rst

@@ -5454,7 +5454,7 @@ types, where they are relevant.  Some of these are not reported by the
   ``__base__`` is the base class that is involved in that chain.
 
   .. note::
-    The behavior of the ``__base__`` attribute is dependent on the CPython implementation.
+    The behavior of the ``__base__`` attribute is dependent on the :term:`CPython` implementation.
 
 .. attribute:: definition.__name__
 

Doc/reference/datamodel.rst

@@ -861,7 +861,7 @@ Custom classes
           ``__base__`` is the base class that is involved in that chain.
 
           .. note::
-            The behavior of the ``__base__`` attribute is dependent on the CPython implementation.
+            The behavior of the ``__base__`` attribute is dependent on the :term:`CPython` implementation.
 
       :attr:`__doc__`
          The class's documentation string, or ``None`` if undefined.