[ecashaddrjs] Update licensing refs

Summary:
T3039

Depends on D13476

Update licensing and repo refs to ABC info

Test Plan: Confirm changes are only to comments. Confirm info is correct.

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D13477