Remove outdated coupons banner from coupon list screen

[JorgeMucientes]

Cloned from Android: https://github.com/woocommerce/woocommerce-android/issues/12956

Coupons feature has been enabled for more than a year now. The current banner from the screen feels outdated and doesn't make sense anymore. Also the banner is shown when the search icon is tapped.

[dangermattic]

Thanks for reporting! 👍