No longer allow nil type namespace factories

All default namespace factories should be `UserNamespace`
since `nil` used to mean `User` type

ee/spec/services/compliance_management/frameworks/create_service_spec.rb

@@ -3,7 +3,7 @@
 require 'spec_helper'
 
 RSpec.describe ComplianceManagement::Frameworks::CreateService do
-  let_it_be_with_refind(:namespace) { create(:namespace) }
+  let_it_be_with_refind(:namespace) { create(:user_namespace) }
 
   let(:params) do
     {

ee/spec/services/compliance_management/frameworks/destroy_service_spec.rb

@@ -3,7 +3,7 @@
 require 'spec_helper'
 
 RSpec.describe ComplianceManagement::Frameworks::DestroyService do
-  let_it_be_with_refind(:namespace) { create(:namespace) }
+  let_it_be_with_refind(:namespace) { create(:user_namespace) }
   let_it_be_with_refind(:framework) { create(:compliance_framework, namespace: namespace) }
 
   context 'when feature is disabled' do

ee/spec/services/compliance_management/frameworks/update_service_spec.rb

@@ -3,7 +3,7 @@
 require 'spec_helper'
 
 RSpec.describe ComplianceManagement::Frameworks::UpdateService do
-  let_it_be_with_refind(:namespace) { create(:namespace) }
+  let_it_be_with_refind(:namespace) { create(:user_namespace) }
   let_it_be_with_refind(:framework) { create(:compliance_framework, namespace: namespace) }
 
   let(:current_user) { namespace.owner }

spec/models/namespace_spec.rb

@@ -284,7 +284,7 @@ RSpec.describe Namespace do
       end
     end
 
-    context 'creating a default Namespace' do
+    context 'creating a Namespace with nil type' do
       let(:namespace_type) { nil }
 
       it 'is the correct type of namespace' do
@@ -295,7 +295,7 @@ RSpec.describe Namespace do
     end
 
     context 'creating an unknown Namespace type' do
-      let(:namespace_type) { 'One' }
+      let(:namespace_type) { 'nonsense' }
 
       it 'creates a default Namespace' do
         expect(Namespace.find(namespace.id)).to be_a(Namespace)