bug#51006: 28.0.60; Slowness while navigating in inferior-python-mode

[Simen Heggestøyl]

This seems to have been fixed on master by:

commit ab34293d849086a67effc52800e18bab1400ce72
Author: Lars Ingebrigtsen <larsi@gnus.org>
Date:   Wed Oct 13 18:44:35 2021 +0200

    Fix problem with multiline fontification in interactive Python
    
    * lisp/progmodes/python.el
    (python-shell-font-lock-post-command-hook): When doing multi-line
    (`C-c SPC') inputs, remove all the preceding lines when doing
    fontification (bug#47657).

Should it be backported to emacs-28 as the problem still exists there?

Otherwise I think this bug can be closed.