REST API: Specify specific json-schema version.

Explicitly specifies that the REST API uses JSON Schema draft-04,
as JSON Schema has deprecated versionless schema URIs and recommends
the use of a specific draft version.

Props @TimothyBlynJacobs
Fixes #41734



git-svn-id: https://develop.svn.wordpress.org/trunk@41731 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/rest-api/endpoints/class-wp-rest-users-controller.php

@@ -1129,7 +1129,7 @@ class WP_REST_Users_Controller extends WP_REST_Controller {
 	 */
 	public function get_item_schema() {
 		$schema = array(
-			'$schema'    => 'http://json-schema.org/schema#',
+			'$schema'    => 'http://json-schema.org/draft-04/schema#',
 			'title'      => 'user',
 			'type'       => 'object',
 			'properties' => array(