[explorer] Show the correct unit in the faucet

Summary: Upon successful sent the explorer message advertises that 1,000,000 tXEC have been sent. But the returned amount is in satoshis so it should display 10,000.00 tXEC instead.

Test Plan: Check in preview

Reviewers: #bitcoin_abc, bytesofman

Reviewed By: #bitcoin_abc, bytesofman

Differential Revision: https://reviews.bitcoinabc.org/D16989