gh-117339: Use NULL instead of None for LOAD_SUPER_ATTR in dis docs (GH-117343)

Author: Christopher-Chianelli

Doc/library/dis.rst

@@ -1224,7 +1224,7 @@ iterations of the loop.
    except that ``namei`` is shifted left by 2 bits instead of 1.
 
    The low bit of ``namei`` signals to attempt a method load, as with
-   :opcode:`LOAD_ATTR`, which results in pushing ``None`` and the loaded method.
+   :opcode:`LOAD_ATTR`, which results in pushing ``NULL`` and the loaded method.
    When it is unset a single value is pushed to the stack.
 
    The second-low bit of ``namei``, if set, means that this was a two-argument