pythongh-119016: Remove outdated sentences from the "classes" tutorial (

python#119130)

Co-authored-by: Alex Waygood <[email protected]>

Doc/tutorial/classes.rst

@@ -338,11 +338,7 @@ code will print the value ``16``, without leaving a trace::
    del x.counter
 
 The other kind of instance attribute reference is a *method*. A method is a
-function that "belongs to" an object.  (In Python, the term method is not unique
-to class instances: other object types can have methods as well.  For example,
-list objects have methods called append, insert, remove, sort, and so on.
-However, in the following discussion, we'll use the term method exclusively to
-mean methods of class instance objects, unless explicitly stated otherwise.)
+function that "belongs to" an object.
 
 .. index:: pair: object; method