Добавляем в functions.php:
add_filter( 'get_the_archive_title', function ($title) {
if ( is_category() ) {
$title = single_cat_title( '', false );
} elseif ( is_tag() ) {
$title = single_tag_title( '', false );
} elseif ( is_author() ) {
$title = '' . get_the_author() . '' ;
}
return $title;
});