[Cashtab] Stop using a function that isnt really used in SignVerify component

Summary:
We don't support params in this screen so we should not be using the parseAddressForParams function. We are just passing user input there to get it back in an object at the address key.

Stop doing this.

Ref D15134 for the bigger picture here -- we need more granular info in the parseAddressForParams function to support additional bip21 parameters like opreturn

Test Plan:
npm test

npm start, navigate to sign verify screen, paste a valid ecash: address in verify box and note no validation, paste an invalid address and note error msg, paste an etoken: addr and note error msg

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Subscribers: emack

Differential Revision: https://reviews.bitcoinabc.org/D15135