fix sourcemap test

packages/svelte/tests/sourcemaps/samples/css-injected-map/_config.js

@@ -30,10 +30,10 @@ export default test({
 	async test({ assert, code_client }) {
 		// Check that the css source map embedded in the js is accurate
 		const match = code_client.match(
-			/append_styles\(\$\$anchor, "svelte-.{6}", "(.*?)(?:\\n\/\*# sourceMappingURL=data:(.*?);charset=(.*?);base64,(.*?) \*\/)?"\);/
+			/code: "(.*?)(?:\\n\/\*# sourceMappingURL=data:(.*?);charset=(.*?);base64,(.*?) \*\/)?"/
 		);
 
-		assert.notEqual(match, null);
+		assert.ok(match);
 
 		const [css, mime_type, encoding, css_map_base64] = /** @type {RegExpMatchArray} */ (
 			match