[Cashtab] Correct proptypes validation for settings

Summary:
T2281

This prop is initialized as false as part of loading the parameter and validating it. This diff adjusts the proptypes validation to accept bool as well as object

Test Plan:
npm start from master and see react proptype error in dev console.
npm start from this branch and see react proptype error is gone

Reviewers: #bitcoin_abc, kieran709

Reviewed By: #bitcoin_abc, kieran709

Differential Revision: https://reviews.bitcoinabc.org/D11124