REST API: Add uniqueItems as a permitted endpoint argument JSON Schema keyword.

Support for the `uniqueItems` keyword was added in [48357], but wasn't included in the list of permitted keywords for `WP_REST_Controller::get_endpoint_args_for_item_schema()`. This prevented the keyword from being automatically supported if specified in a controller's item schema.

Props TimothyBlynJacobs.
Merges [48796] to the 5.5 branch.
Fixes #51021.
Built from https://develop.svn.wordpress.org/branches/5.5@48807


git-svn-id: http://core.svn.wordpress.org/branches/5.5@48569 1a063a9b-81f0-0310-95a4-ce76da25c4cd

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

@@ -645,6 +645,7 @@ abstract class WP_REST_Controller {
 			'pattern',
 			'minItems',
 			'maxItems',
+			'uniqueItems',
 		);
 
 		foreach ( $schema_properties as $field_id => $params ) {

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.5.1-alpha-48806';
+$wp_version = '5.5.1-alpha-48807';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.