Fix ci subscriptions project spec

We need to pass in a downstream project because we call
`subject.dup.save` in the spec and `dup` won't duplicate the unsaved
association.

Passing in a persisted model means calling `dup` would just copy over
the same `downstream_project_id`.

ee/spec/models/ci/subscriptions/project_spec.rb

@@ -3,7 +3,8 @@
 require 'spec_helper'
 
 RSpec.describe Ci::Subscriptions::Project do
-  let(:upstream_project) { create(:project, :public) }
+  let_it_be(:upstream_project) { create(:project, :public) }
+  let_it_be(:downstream_project) { create(:project) }
 
   describe 'Relations' do
     it { is_expected.to belong_to(:downstream_project).required }
@@ -11,7 +12,7 @@ RSpec.describe Ci::Subscriptions::Project do
   end
 
   it_behaves_like 'includes Limitable concern' do
-    subject { build(:ci_subscriptions_project, upstream_project: upstream_project) }
+    subject { build(:ci_subscriptions_project, upstream_project: upstream_project, downstream_project: downstream_project) }
   end
 
   describe 'Validations' do