bpo-33387: update documentation for exception handling opcode changes (GH-24334)

* bpo-33387: remove obsolete comment

* bpo-33387: update SETUP_WITH opcode documentation
diff --git a/Doc/library/dis.rst b/Doc/library/dis.rst
index c09d833..f3b2538 100644
--- a/Doc/library/dis.rst
+++ b/Doc/library/dis.rst
@@ -742,7 +742,7 @@
 
    This opcode performs several operations before a with block starts.  First,
    it loads :meth:`~object.__exit__` from the context manager and pushes it onto
-   the stack for later use by :opcode:`WITH_CLEANUP_START`.  Then,
+   the stack for later use by :opcode:`WITH_EXCEPT_START`.  Then,
    :meth:`~object.__enter__` is called, and a finally block pointing to *delta*
    is pushed.  Finally, the result of calling the ``__enter__()`` method is pushed onto
    the stack.  The next opcode will either ignore it (:opcode:`POP_TOP`), or