Change doctest to python codeblock in Annotate class recipe

Author: dr-carlos

Doc/library/annotationlib.rst

@@ -559,15 +559,15 @@ used with all formats, and takes advantage of class encapsulation:
 
 This can then be called with:
 
-.. doctest::
+.. code-block:: python
 
    >>> from annotationlib import call_annotate_function, Format
    >>> call_annotate_function(Annotate(), format=Format.STRING)
    {'x': 'MyType'}
 
 Or used as the annotate function for an object:
 
-.. doctest::
+.. code-block:: python
 
    >>> from annotationlib import get_annotations, Format
    >>> class C: