Fix shopping cart UI

In both device form factors with and without home buttons, the nav bar area is probably set to "clear" color, which makes it appear as black: 
<img width="546" alt="image" src="https://github.com/sentry-demos/ios/assets/3241469/a788930f-5df4-4cbe-a64e-8bf376b30d2a">
<img width="561" alt="image" src="https://github.com/sentry-demos/ios/assets/3241469/c23cbe37-2b9d-4be4-849f-6eb1b57ede38">
