remove duplicate required

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

@@ -78,7 +78,6 @@ public function register_routes() {
 					'args'                => array(
 						'slug'            => array(
 							'description' => __( 'The slug of the template to get the fallback for' ),
-							'required' => true,
 							'type'        => 'string',
 							'required'    => true,
 						),