[Cashtab] Remove proptypes from component with no props

Summary: Leftover or copypasta. This component does not use props so does not need proptypes.

Test Plan: npm test

Reviewers: #bitcoin_abc, PiRK, emack

Reviewed By: #bitcoin_abc, PiRK, emack

Differential Revision: https://reviews.bitcoinabc.org/D15561