function plt_hide_metadata_viewer_metaboxes() {
$screen = get_current_screen();
if ( !$screen ) {
return;
}
//Hide the "Post Metadata Viewer" meta box.
remove_meta_box('post-metadata-viewer', $screen->id, 'normal');
}
add_action('add_meta_boxes', 'plt_hide_metadata_viewer_metaboxes', 20);