Update auth instructions to work around problem with new portraits

[dsjoerg]

If we do #30 this is no longer necessary or relevant.

Every time Blizzard adds new portraits, we get complaints from users who can't authenticate. That's because when Blizzard adds new portraits we have to make code and asset changes to take them in.

So as a quick & easy fix we could change the instructions to tell the person to first change their portrait to one of the standard ones like Kachinsky, and then wait and continue with the standard process. Or we could simply tell them to change their portrait TO Kachinsky unless it's already Kachinsky, in which case we tell them to change it to another one of the standard ones.