Disable m4a and m4b type in wordpress upload

function.php

<?php
/**
 * Modify mime types
 * @param  array $mime_types Mime types
 */
public function modify_mime_type($mime_types){
  // Unset m4a type
  unset( $mime_types['mp3|m4a|m4b'] );

  // Added mp3 type
  $mime_types['mp3'] = 'audio/mp3';

  return $mime_types;
}
add_filter( 'upload_mimes', 'modify_mime_type' );