Update flip parameter description in WP REST Attachments Controller and corresponding test fixture to remove unnecessary details.

Author: ramonjd

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

@@ -1558,7 +1558,7 @@ protected function get_edit_media_item_args() {
 									),
 									'properties'  => array(
 										'flip' => array(
-											'description' => __( 'Flip direction. [ horizontal, vertical ]' ),
+											'description' => __( 'Flip direction.' ),
 											'type'        => 'object',
 											'required'    => array(
 												'horizontal',

tests/qunit/fixtures/wp-api-generated.js

@@ -3445,7 +3445,7 @@ mockedApiResponse.Schema = {
                                                 ],
                                                 "properties": {
                                                     "flip": {
-                                                        "description": "Flip direction. [ horizontal, vertical ]",
+                                                        "description": "Flip direction.",
                                                         "type": "object",
                                                         "required": [
                                                             "horizontal",