[Cashtab] Remove rename active wallet option from header

Summary: We can now rename the active wallet normally from the settings screen. I do not think this feature is used often enough to warrant a prominent place in the header on every single screen.

Test Plan: npm test

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D15658