MySQL 8.0 Release Notes
MySQL 8.0 Source Code Documentation
TheDROP FUNCTION
statement is used to drop stored functions and loadable functions:
For information about dropping stored functions, seeSection 13.1.29, “DROP PROCEDURE and DROP FUNCTION Statements”.
For information about dropping loadable functions, seeSection 13.7.4.2, “DROP FUNCTION Statement for Loadable Functions”.