Docs: replace an esoteric Von Neumann mention (GH-137598)

* Docs: replace an esoteric Von Neumann mention

* oops, don't need to edit topics.py
(cherry picked from commit 237dca5)

Co-authored-by: Ned Batchelder <[email protected]>

Author: nedbat

Doc/reference/datamodel.rst

@@ -16,9 +16,8 @@ Objects, values and types
    single: data
 
 :dfn:`Objects` are Python's abstraction for data.  All data in a Python program
-is represented by objects or by relations between objects. (In a sense, and in
-conformance to Von Neumann's model of a "stored program computer", code is also
-represented by objects.)
+is represented by objects or by relations between objects. Even code is
+represented by objects.
 
 .. index::
    pair: built-in function; id
@@ -29,9 +28,6 @@ represented by objects.)
    single: mutable object
    single: immutable object
 
-.. XXX it *is* now possible in some cases to change an object's
-   type, under certain controlled conditions
-
 Every object has an identity, a type and a value.  An object's *identity* never
 changes once it has been created; you may think of it as the object's address in
 memory.  The :keyword:`is` operator compares the identity of two objects; the