FEATURE REMOVAL: persona login

see: https://meta.discourse.org/t/pulling-persona-out-of-discourse-core/12613

lib/auth/persona_authenticator.rb

@@ -1,25 +0,0 @@
-class Auth::PersonaAuthenticator < Auth::Authenticator
-
-  def name
-    "persona"
-  end
-
-  # TODO twitter provides all sorts of extra info, like website/bio etc.
-  #  it may be worth considering pulling some of it in.
-  def after_authenticate(auth_token)
-    result = Auth::Result.new
-
-    result.email = email = auth_token[:info][:email]
-    result.email_valid = true
-
-    result.user = User.find_by_email(email)
-    result
-  end
-
-  def register_middleware(omniauth)
-    omniauth.provider :browser_id,
-           :name => "persona"
-  end
-end
-
-