Add conditional so we only show the featured comment button on comments

Applies to https://github.com/GigaOM/gigaom/issues/5132
You can't use the pattern in https://github.com/GigaOM/go-marketo/blob/master/components/class-go-marketo-admin.php#L51 ?

```php
	public function admin_enqueue_scripts( $hook )
	{
		if ( 'user-edit.php' == $hook )
		{
			wp_enqueue_script( 'go_marketo_admin_js', plugins_url( '/js/go-marketo-admin.js', __FILE__ ), array( 'jquery' ), $this->core->version, TRUE );
		}
	}//END admin_enqueue_scripts