[Cashtab] Remove repeated and unnecessary specialized styled component

Summary:
Depends on D17034

Initially I thought this div would need more special treatment. But just adding some margintop is not a good reason to keep this distinct styled component, esp now that the component already has this margin top.

Test Plan: npm test

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D17035