[tests] bump timeout for receiving proof in get_ava_p2p_interface

Summary: I saw a CI failure due to a proof being received after 3 seconds: https://reviews.bitcoinabc.org/D13097#290754

Test Plan: ninja check-functional

Reviewers: #bitcoin_abc, sdulfari

Reviewed By: #bitcoin_abc, sdulfari

Subscribers: sdulfari

Differential Revision: https://reviews.bitcoinabc.org/D13099