[fix] add 'categories' to PYLINT_ADDITIONAL_BUILTINS_FOR_ENGINES

androp no longer needed (see line 591 in 7b235a1c)::

    # pylint: disable=undefined-variable

Suggested-by: @dalf https://github.com/searxng/searxng/issues/102#issuecomment-914068609


Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>