Fix Style/OpenStructUse offenses

Changelog: other

.rubocop_todo/style/open_struct_use.yml

@@ -26,7 +26,6 @@ Style/OpenStructUse:
   - spec/graphql/mutations/commits/create_spec.rb
   - spec/helpers/application_settings_helper_spec.rb
   - spec/helpers/profiles_helper_spec.rb
-  - spec/initializers/doorkeeper_spec.rb
   - spec/lib/gitlab/auth/o_auth/provider_spec.rb
   - spec/lib/gitlab/database/migrations/runner_spec.rb
   - spec/lib/gitlab/gitaly_client/blobs_stitcher_spec.rb

spec/initializers/doorkeeper_spec.rb

@@ -24,7 +24,7 @@ RSpec.describe Doorkeeper.configuration do
     before do
       allow(controller).to receive(:current_user).and_return(current_user)
       allow(controller).to receive(:session).and_return({})
-      allow(controller).to receive(:request).and_return(OpenStruct.new(fullpath: '/return-path'))
+      allow(controller).to receive(:request).and_return(double('request', fullpath: '/return-path'))
       allow(controller).to receive(:redirect_to)
       allow(controller).to receive(:new_user_session_url).and_return('/login')
     end