docs(navigation): Use createNavigationContainerRef instead of React.useRef (#14299)

## DESCRIBE YOUR PR

This PR fixes an incorrect example in the documentation where
`React.useRef()` was used with `NavigationContainer`.

React Navigation requires using `createNavigationContainerRef()` instead
of `React.useRef()` to ensure proper access to navigation methods from
outside React components.

This change ensures consistency with React Navigation's official
recommendation and prevents potential issues when performing
programmatic navigation.

Fixes: N/A

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## EXTRA RESOURCES

- [Sentry Docs contributor guide](https://docs.sentry.io/contributing/)

Author: rigAITe

includes/react-native-react-navigation-setup.mdx

@@ -1,6 +1,6 @@
 ```jsx {5, 20} {tabTitle: Functional Components}
 import * as Sentry from "@sentry/react-native";
-import { NavigationContainer } from "@react-navigation/native";
+import { NavigationContainer, createNavigationContainerRef } from "@react-navigation/native";
 
 const navigationIntegration = Sentry.reactNavigationIntegration({
   enableTimeToInitialDisplay: true,
@@ -12,7 +12,7 @@ Sentry.init({
 })
 
 function App = () => {
-  const containerRef = React.useRef();
+  const containerRef = createNavigationContainerRef();
 
   return (
     <NavigationContainer
@@ -39,7 +39,7 @@ Sentry.init({
 })
 
 class App extends React.Component {
-  containerRef = React.createRef();
+  containerRef = createNavigationContainerRef();
 
   render() {
     return (