Use correct default mode in Node OnUnhandledRejection integration (#13132)

resolves #12074

Author: AbhiPrasad

docs/platforms/javascript/common/configuration/integrations/unhandledrejection.mdx

@@ -91,4 +91,4 @@ mimics the behavior of [node's](https://nodejs.org/api/cli.html#--unhandled-reje
 - `warn`: Always trigger a warning, no matter if the unhandledRejection hook is set or not but do not print the deprecation warning.
 - `none`: Silence all warnings.
 
-Defaults to `none`.
+Defaults to `warn`.