Today, we close the connection after 10 errors. While this is fine for
normal use, it is unnecessarily large.
Lowering it to 3 helps with defense-in-depth for cross-protocol attacks
(e.g. https://alpaca-attack.com/), while still being large enough for
useful troubleshooting and normal operation.
As part of this change, we also remove the AUTH-specific failures limit,
because they're covered by the connection limit.
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