[avalanche] Reduce remote proofs verbosity

Summary: The proofs are requested every few minutes from all our peers, so logging the remote proofs is giving little information but creates a lot of noise in the log.

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D15127