GUI: Receive: Remove option to reuse a previous address

Summary:
This was justified by the need to "resent" an invoice, but now that we have the request history, that need should be gone.

Backports PR3716
https://github.com/bitcoin/bitcoin/pull/3716/

Completes T599

Test Plan:
make check
bitcoin-qt
Under the receive tab, there should be no option to reuse an existing receiving address.

Reviewers: jasonbcox, deadalnix, Fabien, O1 Bitcoin ABC, #bitcoin_abc

Reviewed By: jasonbcox, O1 Bitcoin ABC, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D2805