Presumably there's nothing about your deposit account or fee that implicates Regulation Z. Regulation DD requires that you provide advance notice "if the change may reduce the annual percentage yield or adversely affect the consumer." [12 CFR Part 230, ยง
230.5(a)(1)] So, if the only change you're making is the elimination of the daily fee, you would not have to provide an advance notice. You would, however, need to update your current disclosures and fee schedules, including any disclosure you might make in order to solicit opt-ins for an overdraft service that covers ATM or one-time debit card transactions.
That said, if my bank decided to do away with a fee, I'd expect it to "blow its own horn" and notify me of the good news. There would be no 30-day timing requirement.
Now, if you're at the same time raising your transactional OD fee to offset the expected loss of income from your erstwhile daily OD fee, you'd have to provide 30 days' notice of the increase.