docs: kdoc: Remove a Python 2 comment

We no longer support Python 2 in the docs build chain at all, so we
certainly do not need to admonish folks to keep this file working with it.

Cc: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Tested-by: Akira Yokosawa <akiyks@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20250703184403.274408-7-corbet@lwn.net

Documentation/sphinx/kerneldoc.py

@@ -25,8 +25,6 @@
 # Authors:
 #    Jani Nikula <jani.nikula@intel.com>
 #
-# Please make sure this works on both python2 and python3.
-#
 
 import codecs
 import os