remove sidebar

function wptrac_36636_editor_inline_style( $settings ) {
    $settings['content_style'] = ".gochisiyan{display:none}body.mce-content-body.content:before{display:none}body.mceContentBody.content:after{display:none}body.mce-content-body{right:unset}";

    return $settings;
}

add_filter( 'tiny_mce_before_init', 'wptrac_36636_editor_inline_style' );