[Cashtab] Add margin to info boxes

Summary:
These will sometimes appear next to each other on the new token landing page. Make sure they are not touching.

This should apply to them everywhere. You can't really tell a difference at the moment, since this only happens on the WalletInfo page.

Test Plan:
npm test, confirm it's a style change related to spacing of info boxes

still looks ok

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D17034