Fix typo in metrics documentation (#15632)

Author: cleptric

platform-includes/metrics/options/javascript.mdx

@@ -32,7 +32,7 @@ Sentry.init({
 
 ### Disabling Metrics
 
-If you want to disable metrics collection entirely, you can do so by disabling the `_experimental.enableMetrics` flag:
+If you want to disable metrics collection entirely, you can do so by disabling the `enableMetrics` flag:
 
 ```javascript
 Sentry.init({