p2p: Don't send FEEFILTER in blocksonly mode

Summary:
It is unnecessary to send FEEFILTER messages when we don't accept
transactions from our peers.

This is a backport of core#21509

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D12182