Remove `SessionsController#authenticate_with_two_factor`.

- This was abstracted into the `AuthenticatesWithTwoFactor` module, but
  was probably resurrected during a merge.

app/controllers/sessions_controller.rb

@@ -91,27 +91,6 @@ class SessionsController < Devise::SessionsController
     find_user.try(:two_factor_enabled?)
   end
 
-  def authenticate_with_two_factor
-    user = self.resource = find_user
-
-    if user_params[:otp_attempt].present? && session[:otp_user_id]
-      if valid_otp_attempt?(user)
-        # Remove any lingering user data from login
-        session.delete(:otp_user_id)
-
-        remember_me(user) if user_params[:remember_me] == '1'
-        sign_in(user) and return
-      else
-        flash.now[:alert] = 'Invalid two-factor code.'
-        render :two_factor and return
-      end
-    else
-      if user && user.valid_password?(user_params[:password])
-        prompt_for_two_factor(user)
-      end
-    end
-  end
-
   def gitlab_geo_login
     return unless Gitlab::Geo.secondary?
     return if signed_in?