Update copy of Hive badge award email

Copy updated to match https://docs.google.com/document/d/1glUi-d0yTaEM1f_PZzm8bQ9guamBqCAKWgzagSBA_9U/edit#
That makes sense. I admit I was largely just blindly following the copy.  I assumed the removal of the "is this person already a user?" logic was intended, since the copy was changed such that it makes sense whether or not you have an account.  That's probably an incorrect assumption though, will change.