[3.13] gh-138011: Clarify tutorial method object example code (GH-138014) (#138026)

x must be a MyClass instance for examples to work.

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(cherry picked from commit 339f5da639)

Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>

Doc/tutorial/classes.rst

@@ -359,7 +359,7 @@ Usually, a method is called right after it is bound::
 
    x.f()
 
-In the :class:`!MyClass` example, this will return the string ``'hello world'``.
+If ``x = MyClass()``, as above, this will return the string ``'hello world'``.
 However, it is not necessary to call a method right away: ``x.f`` is a method
 object, and can be stored away and called at a later time.  For example::