Remove FF ci_resource_group

This commit removes the FF

app/models/ci/build.rb

@@ -486,7 +486,6 @@ module Ci
     end
 
     def requires_resource?
-      Feature.enabled?(:ci_resource_group, project, default_enabled: true) &&
       self.resource_group_id.present?
     end
 

lib/gitlab/ci/pipeline/seed/build/resource_group.rb

@@ -16,7 +16,6 @@ module Gitlab
             end
 
             def to_resource
-              return unless Feature.enabled?(:ci_resource_group, build.project, default_enabled: true)
               return unless resource_group_key.present?
 
               resource_group = build.project.resource_groups