postmatic-multiauthor-remove-single-filter.php

<?php
function postmatic_multiauthor_remove_single_filter() {
	if ( ! class_exists( 'Postmatic_Multi_Author' ) ) {
		return;
	}
	remove_filter(
		'prompt/subscribe_widget_object',
		array( Postmatic_Multi_Author::get_instance(), 'filter_subscribe_widget_object' )
	);
}
add_action( 'init', 'postmatic_multiauthor_remove_single_filter', 20 );