fix: correct server condition in withStorybook function, see #877 (comment)

- Updated the condition to disable experimental MCP settings when the server is not present, ensuring proper configuration behavior.
- This change enhances the reliability of the withStorybook function in various environments.

All tests pass successfully.

Author: ndelangen

packages/react-native/src/withStorybook.ts

@@ -87,7 +87,7 @@ export function withStorybook<T>(config: T, options: WithStorybookOptions = {}):
   );
   const settings = { ...options };
 
-  if (server) {
+  if (!server) {
     settings.experimental_mcp = false;
   }