modelize: do not warn `useless-type` for a covariant redefinition of a getter return type.

Signed-off-by: Jean Privat <jean@pryen.org>
typing: warn `useless-type` for useless type in a local variable

Signed-off-by: Jean Privat <jean@pryen.org>
lib/standard: remove 3 useless types in local variables

Signed-off-by: Jean Privat <jean@pryen.org>