Disable "confirm your new account" activation email for invitees

[techAPJ (Arpit Jalan)]

@gerhard fixed this per:

Allow disabling activation email for invited users

This is finally done. Users invited via email won’t receive another email to activate their account. Their email address will be marked as verified as soon as they accept the invite. Users invited via link won’t be logged in automatically after accepting the invite. They will get another email to verify their email address before they will be able to login. https://github.com/discourse/discourse/commit/7977b09025751973f7ae1271f68aaab2716e01fa