lib: add note about removing sys module
I was about to remove this module and luckily I found #49520 before that. So, I think adding this note might prevent this year after year :)
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
I was about to remove this module and luckily I found #49520 before that. So, I think adding this note might prevent this year after year :)