docs: fix Golden Retriever service worker import (#5425)

docs/golden-retriever.mdx

@@ -106,7 +106,7 @@ store references to large files.
    :::
 
    ```js title="sw.js"
-   import('@uppy/golden-retriever/lib/ServiceWorker');
+   import '@uppy/golden-retriever/lib/ServiceWorker';
    ```
 
 2. Register it in your app’s entry point: