docs(js): Fix browserTracingIntegration usage to prevent error (#11133)

Author: charpeni

platform-includes/performance/group-transaction-example/javascript.mdx

@@ -19,7 +19,7 @@ import * as Sentry from "@sentry/browser";
 Sentry.init({
   // ...
   integrations: [
-    browserTracingIntegration({
+    Sentry.browserTracingIntegration({
       beforeStartSpan: (context) => {
         return {
           ...context,