disallow-file-edit-wordpress

In wp-config.php

define('DISALLOW_FILE_EDIT', true);

define('DISALLOW_FILE_MODS', true);

OR

In Functions.php

function disable_mytheme_action() {

  define('DISALLOW_FILE_EDIT', true);

  define('DISALLOW_FILE_MODS', true);

}
add_action('init','disable_mytheme_action');