Remove design_management_todos_api feature flag

https://gitlab.com/gitlab-org/gitlab/issues/32492

ee/lib/ee/api/todos.rb

@@ -18,16 +18,6 @@ module EE
           def authorize_can_read!
             authorize!(:read_epic, epic)
           end
-
-          override :find_todos
-          def find_todos
-            todos = super
-
-            return todos if ::Feature.enabled?(:design_management_todos_api, default_enabled: true)
-
-            # Exclude Design Todos if the feature is disabled
-            todos.where.not(target_type: ::DesignManagement::Design.name) # rubocop: disable CodeReuse/ActiveRecord
-          end
         end
 
         resource :groups, requirements: ::API::API::NAMESPACE_OR_PROJECT_REQUIREMENTS do

ee/spec/requests/api/todos_spec.rb

@@ -75,7 +75,6 @@ describe API::Todos do
         get api('/todos', personal_access_token: pat)
       end
 
-      context 'when the feature is enabled' do
       before do
         api_request
       end
@@ -96,20 +95,6 @@ describe API::Todos do
         )
       end
     end
-
-      context 'when the feature is disabled' do
-        before do
-          stub_feature_flags(design_management_todos_api: false)
-          api_request
-        end
-
-        it_behaves_like 'an endpoint that responds with success'
-
-        it 'does not include the Design Todo in the response' do
-          expect(json_response).to be_empty
-        end
-      end
-    end
   end
 
   describe 'POST :id/epics/:epic_iid/todo' do

lib/api/todos.rb

@@ -13,13 +13,6 @@ module API
       'issues' => ->(iid) { find_project_issue(iid) }
     }.freeze
 
-    helpers do
-      # EE::API::Todos would override this method
-      def find_todos
-        TodosFinder.new(current_user, params).execute
-      end
-    end
-
     params do
       requires :id, type: String, desc: 'The ID of a project'
     end
@@ -48,6 +41,10 @@ module API
 
     resource :todos do
       helpers do
+        def find_todos
+          TodosFinder.new(current_user, params).execute
+        end
+
         def issuable_and_awardable?(type)
           obj_type = Object.const_get(type, false)