Truncate very old, overlong Maniphest mail keys
Ref T1191. Long ago, Maniphest generated with 40-character mail keys. These prevent the migration to bytes20. We had about 300 of these on secure.phabricator.com from several years ago.
Just truncate them. This adjusts reply-to addresses, but it's very likely that none are relevant anymore.
Test Plan: Ran migration on secure.phabricator.com to truncate keys.
Reviewed By: btrahan
Maniphest Tasks: T1191
Differential Revision: https://secure.phabricator.com/D10615