Align alphlisting_styles callback with three-arg filter

[Lin87]

The return_styles callback now only accepts $styles, but the hook above still registers it with accepted_args = 3 and Query::get_customized_column_styles continues to call apply_filters('alphalisting_styles', '', $this, $this->instance_id) with three arguments. Under PHP 8 this produces a TypeError (“3 passed and exactly 1 expected”) whenever column styles are rendered, crashing the shortcode/block. The same arity mismatch exists in ColumnWidth::return_styles and Columns::return_styles as well.