Renderer: Fix return type in compileAsync method documentation (#32205)

* Renderer: Fix return type in compileAsync method documentation

* Review comment: https://github.com/mrdoob/three.js/pull/32205#discussion_r2502265739

src/renderers/common/Renderer.js

@@ -835,7 +835,7 @@ class Renderer {
 	 * @param {Object3D} scene - The scene or 3D object to precompile.
 	 * @param {Camera} camera - The camera that is used to render the scene.
 	 * @param {?Scene} targetScene - If the first argument is a 3D object, this parameter must represent the scene the 3D object is going to be added.
-	 * @return {Promise<Array|undefined>} A Promise that resolves when the compile has been finished.
+	 * @return {Promise} A Promise that resolves when the compile has been finished.
 	 */
 	async compileAsync( scene, camera, targetScene = null ) {