Remove unused `another_email` factory

spec/factories/emails.rb

 FactoryGirl.define do
   factory :email do
     user
-    email do
-      FFaker::Internet.email('alias')
-    end
-
-    factory :another_email do
-      email do
-        FFaker::Internet.email('another.alias')
-      end
-    end
+    email { FFaker::Internet.email('alias') }
   end
 end