[Cashtab] [Address simplification p2/4] Stop converting to legacy format for Burn Token

Summary:
T2730

Depends on D12651

Stop converting burn outputs to legacy address format. Transaction builder will work with existing format (which is cashAddress, to be corrected to ecash: format in a future diff)

Test Plan:
npm start
Do a token burn tx
Sanity check it on block explorer

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D12652