Lower V3AuthVotingInterval back to upstream defaults

Why? Because this makes the Tor network bootstrap way faster (3 times on my
machine).

Why might it OK? This reverts 38eacd13, where we
bumped that value from 10 to 180. Around the same time we did that, Tor folks
bumped that value from 10 to 20, for similar reasons. They did not touch it
since, so it seems it works for them, and there's a chance it works for us too.
And who knows, perhaps the root cause of the problem was in the tor client,
and got fixed since.