You can use the REASSIGN OWNED
command.
Synopsis:
REASSIGN OWNED BY old_role [, ...] TO new_role
This changes all objects owned by old_role
to the new role. You don’t have to think about what kind of objects that the user has, they will all be changed. Note that it only applies to objects inside a single database. It does not alter the owner of the database itself either.
It is available back to at least 8.2. Their online documentation only goes that far back.