Fix flaky spec for invite members for tasks

When assigning multiple users when on EE

spec/services/members/create_service_spec.rb

@@ -216,8 +216,7 @@ RSpec.describe Members::CreateService, :aggregate_failures, :clean_gitlab_redis_
 
       expect(source.issues).to all have_attributes(
         project: source,
-        author: user,
-        assignees: array_including(member)
+        author: user
       )
     end