A person liable to be charged with an offence under section 4, 5, 7 or 30 of the [1988 c. 52.] Road Traffic Act 1988 (drink and drugs) is not liable to be charged under section 12 of the [1872 c. 94.] Licensing Act 1872 with the offence of being drunk while in charge, on a highway or other public place, of a carriage.