Simplify DEWP test

Co-authored-by: Jon Surrell <[email protected]>

packages/dependency-extraction-webpack-plugin/test/fixtures/polyfill-magic-comment/webpack.config.js

@@ -4,11 +4,5 @@
 const DependencyExtractionWebpackPlugin = require( '../../..' );
 
 module.exports = {
-	plugins: [
-		new DependencyExtractionWebpackPlugin( {
-			requestToExternalModule( request ) {
-				return request.startsWith( '@wordpress/' );
-			},
-		} ),
-	],
+	plugins: [ new DependencyExtractionWebpackPlugin() ],
 };