WhatsApp is testing the “Undo delete for me” feature.
WhatsApp is testing a long-due feature to let you Undo deleted messages for a short while if you accidentally deleted a message just for you.
As you can see, this will only work for messages that have been deleted for me and not with the messages that have been deleted for everyone. When you delete a message on your WhatsApp will show a bottom prompt similar to undo status and you can revert the change by pressing that prompt.
Personally, I really like this feature since it has been a long-due feature. And WhatsApp also tested an admin delete feature as well.
Currently, this feature is rolling out to some random testers and this will be available to every on soon.