Remove "metamta.insecure-auth-with-reply-to" Config option

Summary:
Ref T7477. This option was added in D842 in 2011, to support a specific narrow use case at Quora with community moderators using some kind of weird Gmail config.

I don't recall it ever coming up since then, and a survey of a subset of hosted instances (see T11760) reveals that no instances are using this option today. Presumably, even Quora has completed the onboarding discussed in D842, if they still use Phabricator. This option generally does not seem very useful outside of very unusual/narrow cases like the one Quora had.

This would be relatively easy to restore as a local patch if installs do need it, but I suspect this has no use cases anywhere.

Test Plan: Grepped for option, blame-delved to figure out why we added it in the first place, surveyed instances for usage.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T7477

Differential Revision: https://secure.phabricator.com/D19949