Don't return an error if an email can't be found during a password reset

This prevents the ability to harvest email addresses from the HabitRPG database. This solves part of #2867

**Note:** might still be sensitive to timing attacks, but it doesn't seem like it waits for user save or email send (But I'm not an expert).

The `resultMsg` variable is (and was) useless, as client-side only checks for success and shows its own message.

Accompanying habitrpg-shared pull request: #???