Remove expand_names_for_cross_pipeline_artifacts feature flag

It removes the feature flag, enabling the behavior by default.

doc/ci/yaml/README.md

@@ -2164,10 +2164,7 @@ build_job:
 ```
 
 Environment variables support for `project:`, `job:`, and `ref` was [introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/202093)
-in GitLab 13.3. This is under development, but it is ready for production use. It is deployed
-behind the `ci_expand_names_for_cross_pipeline_artifacts` feature flag, which is **disabled by default**.
-[GitLab administrators with access to the GitLab Rails console](../../administration/feature_flags.md)
-can enable it for your instance.
+in GitLab 13.3. [Feature flag removed](https://gitlab.com/gitlab-org/gitlab/-/issues/235761) in GitLab 13.4.
 
 For example:
 

ee/app/models/ee/ci/build_dependencies.rb

@@ -52,9 +52,7 @@ module EE
 
       def build_cross_dependency_relationship_fragment(dependency, search_scope)
         args = dependency.values_at(:job, :ref, :project)
-        if ::Gitlab::Ci::Features.expand_names_for_cross_pipeline_artifacts?(project)
-          args = args.map { |value| ExpandVariables.expand(value, processable_variables) }
-        end
+        args = args.map { |value| ExpandVariables.expand(value, processable_variables) }
 
         dep_id = search_scope.max_build_id_by(*args)
         model_class.id_in(dep_id)

ee/spec/models/ee/ci/build_dependencies_spec.rb

@@ -105,14 +105,6 @@ RSpec.describe Ci::BuildDependencies do
         end
 
         it { is_expected.to contain_exactly(dependency) }
-
-        context 'with the feature flag disabled' do
-          before do
-            stub_feature_flags(ci_expand_names_for_cross_pipeline_artifacts: false)
-          end
-
-          it { is_expected.to be_empty }
-        end
       end
     end