chore(storybook): updated wrapper component in config to match lint rules

Author: travi

.storybook/config.js

@@ -6,15 +6,15 @@ import createPercyAddon from '@percy-io/percy-storybook';
 import {MuiThemeProvider} from '@material-ui/core/styles';
 import {createTheme} from '@travi/travi.org-theme-components';
 
-const Wrapper = ({story}) => {
+function Wrapper({story}) {
   const prefersDarkMode = useMediaQuery('(prefers-color-scheme: dark)');
 
   return (
     <MuiThemeProvider theme={createTheme(prefersDarkMode ? 'dark' : 'light')}>
       {story()}
     </MuiThemeProvider>
   );
-};
+}
 
 addDecorator(story => <Wrapper story={story} />);