[token-server] stop logging ws events

Summary: We are not using the websocket events (yet). Logging was useful for debugging, but, now that the server is handling icons, no reason to print incoming chronik msgs to the log.

Test Plan: npm test

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D15759