[avalanche] Bump the proof vote finalization timeout in the functional test

Summary: The default timeout for the assert_debug_log is 2s, which might be short when waiting for the vote finalization message in the log. Also the event timeout is 60s which is useless since it will fail after 2s anyway.

Test Plan:

for i in {1..100}; do ./test/functional/test_runner.py abc_p2p_avalanche_proof_voting || break; done

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D11054