Remove "Archive" from category page title

Firstly, awesome theme – really, really great.

There are three things I am trying to do but I’ll split them into 3 posts so they can be found more easily if they are solved.

I found a post with this code to remove the word “Archive” from a category archive page, but having put it in my child theme functions.php, nothing changes. I do have other functions in that file that are working.

add_filter('avf_which_archive_output','avf_change_which_archive', 10, 3);
function avf_change_which_archive($output)
{
	if(is_category())
	{
		$output = single_cat_title('',false);
	}

	return $output;
}