Clarify error boundary react behaviour (#9610)

Author: AbhiPrasad

docs/platforms/javascript/guides/react/features/error-boundary.mdx

@@ -28,7 +28,7 @@ Sentry.withErrorBoundary(Example, { fallback: <p>an error has occurred</p> });
 
 <Alert level="warning" title="Note">
 
-In development mode, React will rethrow errors caught within an error boundary. This will result in errors being reported twice to Sentry with the above setup, but this won't occur in your production build.
+In development mode, React will rethrow errors caught within an error boundary to the global error handler. This will result in Sentry only reporting an error from the global error handler, but not from the error boundary itself. We recommend testing the error boundary with a production build of React.
 
 </Alert>