Can the notification "You're over Budget do you want to Approve anyway?" be disabled?

Answer:

There isn't a way to turn off the notification. If the Budget is not being used, closing the Budget would prevent the notification from appearing. Review the following article for details on how to close a Budget. Alternatively, the Budget could be increased, so the overage warning isn't initiated by the approval. Review the following article for instructions on how to update a Budget.