[Cashtab] [BCH deprecation] Pt 1/1 - Deprecate BCH.Address.toCashAddress from cashMethods

Summary:
T2370

The use of BCH.Address.toCashAddress in sendXec() is actually redundant because both outputAddress and destinationAddress variables are already in bch format prior to the call.

Test Plan:
npm test and ensure existing unit test suite passes
npm start
send a simple XEC tx and sense check the tx in explorer
send a one to one XEC tx with unencrypted message
send a one to one XEC tx with encrypted message
send a one to many XEC tx
send a one to many XEC tx with unencrypted message
grep -r 'BCH.Address.toCashAddress' src/ and ensure no further usage of the bch-js function

Reviewers: bytesofman, #bitcoin_abc

Reviewed By: bytesofman, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D12389