WebGPURenderer: Fix instance meshes that shares the same count (#29066)

* WebGPURenderer: Fix instance meshes sharing same count

* cover only instances meshes

src/renderers/common/RenderObject.js

@@ -263,7 +263,7 @@ export default class RenderObject {
 
 		if ( object.count > 1 ) {
 
-			cacheKey += object.count + ',';
+			cacheKey += object.count + ',' + object.uuid + ',';
 
 		}