Rats, not again! A coalition of rattl-ed Brooklynites living on notoriously rodent-infested blocks are pleading with Mayor-elect Zohran Mamdani to bring in a new rat czar – after their calls for the city to renew the fight against the filthy creatures allegedly fell on deaf ears. The pair of Prospect Heights resident groups penned a letter Friday to Mamdani, urging him to reinstate the City Hall rat-fighting position, which was dissolved in September when former Rat Czar Kathleen Corradi