Revise visuals in the payment flow of the `Onboarding` > `Funding a wallet` page.

[pavlenex]

Request the visual

As discussed in #590 this is a follow-up issue where as agreed, we'll look into the payment flow screens and try to revise them if necessary.

Link to the page
https://bitcoin.design/guide/onboarding/funding-a-wallet/)](https://bitcoin.design/guide/onboarding/funding-a-wallet/

[pavlenex]

#604