Remove some mongoid version checks from test suite

We no longer run against or support old Mongoid versions.

test/helpers/devise_helper_test.rb

@@ -34,10 +34,6 @@ class DeviseHelperTest < Devise::IntegrationTest
   end
 
   test 'test errors.messages.not_saved with multiple errors from i18n' do
-    # Dirty tracking behavior prevents email validations from being applied:
-    #    https://github.com/mongoid/mongoid/issues/756
-    (pending "Fails on Mongoid < 2.1"; break) if defined?(Mongoid) && Mongoid::VERSION.to_f < 2.1
-
     get new_user_registration_path
 
     fill_in 'email', with: 'invalid_email'

test/integration/registerable_test.rb

@@ -98,10 +98,6 @@ class RegistrationTest < Devise::IntegrationTest
   end
 
   test 'a guest user cannot sign up with invalid information' do
-    # Dirty tracking behavior prevents email validations from being applied:
-    #    https://github.com/mongoid/mongoid/issues/756
-    (pending "Fails on Mongoid < 2.1"; break) if defined?(Mongoid) && Mongoid::VERSION.to_f < 2.1
-
     get new_user_registration_path
 
     fill_in 'email', with: 'invalid_email'
@@ -120,10 +116,6 @@ class RegistrationTest < Devise::IntegrationTest
   end
 
   test 'a guest should not sign up with email/password that already exists' do
-    # Dirty tracking behavior prevents email validations from being applied:
-    #    https://github.com/mongoid/mongoid/issues/756
-    (pending "Fails on Mongoid < 2.1"; break) if defined?(Mongoid) && Mongoid::VERSION.to_f < 2.1
-
     create_user
     get new_user_registration_path
 

test/support/mongoid.yml

@@ -1,5 +1,5 @@
 test:
-  <%= Mongoid::VERSION.to_i > 4 ? 'clients' : 'sessions' %>:
+  clients:
     default:
       database: devise-test-suite
       hosts: