Collaboration: Remove backward-compatible wp-sync/v1 route alias

The wp-sync/v1 namespace was a transitional alias for the Gutenberg
plugin. Remove it so only wp-collaboration/v1 is registered.

Author: josephfusco

src/wp-includes/collaboration/class-wp-http-polling-collaboration-server.php

@@ -195,20 +195,6 @@ public function register_routes(): void {
 			'/updates',
 			$route_args
 		);
-
-		/*
-		 * Backward-compatible alias so that the Gutenberg plugin's
-		 * bundled sync package (which still uses wp-sync/v1) continues
-		 * to work against WordPress 7.0+.
-		 *
-		 * @todo Remove once the Gutenberg plugin has transitioned to
-		 *       the wp-collaboration/v1 namespace.
-		 */
-		register_rest_route(
-			'wp-sync/v1',
-			'/updates',
-			$route_args
-		);
 	}
 
 	/**