docs: update node-polyfill.mdx (#329)

Author: Timeless0911

website/docs/en/guide/advanced/node-polyfill.mdx

@@ -41,8 +41,6 @@ export default defineConfig({
 
   With the following steps, every usage of the polyfill module will be replaced by the corresponding module in the `externals` field. Checkout the <SourceCode href="https://github.com/web-infra-dev/rslib/blob/main/tests/integration/node-polyfill/bundle-false/rslib.config.ts" /> of the example for more details.
 
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 ## Configurations
 
 Check out the documentation of [@rsbuild/plugin-node-polyfill](https://github.com/rspack-contrib/rsbuild-plugin-node-polyfill), all the configurations are applicable for Rslib.