Fix specs

Author: johnnyshields

spec/mongoid/fields_spec.rb

@@ -1794,15 +1794,15 @@ class DiscriminatorChild2 < DiscriminatorParent
 
       it 'can define a custom type' do
         described_class.configure do
-          type :my_type, Integer
+          define_type :my_type, Integer
         end
 
         expect(described_class::FieldTypes.get(:my_type)).to eq Integer
       end
 
       it 'can override and existing type' do
         described_class.configure do
-          type :integer, String
+          define_type :integer, String
         end
 
         expect(described_class::FieldTypes.get(:integer)).to eq String