gh-93433: Fix dis doc example output (GH-93434)

Doc/library/dis.rst

@@ -6,6 +6,12 @@
 
 **Source code:** :source:`Lib/dis.py`
 
+.. testsetup::
+
+   import dis
+   def myfunc(alist):
+       return len(alist)
+
 --------------
 
 The :mod:`dis` module supports the analysis of CPython :term:`bytecode` by
@@ -37,16 +43,17 @@ Example: Given the function :func:`myfunc`::
        return len(alist)
 
 the following command can be used to display the disassembly of
-:func:`myfunc`::
+:func:`myfunc`:
+
+.. doctest::
 
    >>> dis.dis(myfunc)
-     1           0 RESUME                   0
-
-     2           2 PUSH_NULL
-                 4 LOAD_GLOBAL              1 (NULL + len)
-                 6 LOAD_FAST                0 (alist)
-                 8 CALL                     1
-                18 RETURN_VALUE
+     2           0 RESUME                   0
+   <BLANKLINE>
+     3           2 LOAD_GLOBAL              1 (NULL + len)
+                14 LOAD_FAST                0 (alist)
+                16 CALL                     1
+                26 RETURN_VALUE
 
 (The "2" is a line number).
 
@@ -108,14 +115,15 @@ code.
    .. versionchanged:: 3.11
       Added the ``show_caches`` parameter.
 
-Example::
+Example:
+
+.. doctest::
 
     >>> bytecode = dis.Bytecode(myfunc)
     >>> for instr in bytecode:
     ...     print(instr.opname)
     ...
     RESUME
-    PUSH_NULL
     LOAD_GLOBAL
     LOAD_FAST
     CALL