REST API: Revert widget endpoints

Reverts [50993] as it has missing props.

Reverts [50993].
See #41683.


git-svn-id: https://develop.svn.wordpress.org/trunk@50994 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/widgets/class-wp-widget-recent-posts.php

@@ -26,7 +26,6 @@ class WP_Widget_Recent_Posts extends WP_Widget {
 			'classname'                   => 'widget_recent_entries',
 			'description'                 => __( 'Your site’s most recent Posts.' ),
 			'customize_selective_refresh' => true,
-			'show_instance_in_rest'       => true,
 		);
 		parent::__construct( 'recent-posts', __( 'Recent Posts' ), $widget_ops );
 		$this->alt_option_name = 'widget_recent_entries';