[avalanche] Fix proof voting response type

Summary:
AvalancheVoteError is used for voting on blocks. The tests happen to pass because the underlying integer
is the same as expected. This patch uses the correct AvalancheProofVoteResponse instead.

Test Plan:

./test/functional/test_runner.py abc_p2p_avalanche_proof_voting.py

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D11451