[avalanche] Don't log all the avahello we send

Summary: This log message is redundant with the network log, and brings no value since we send it to all our peers.

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D14820