Remove `:>>` subclass instance declarations
There are not documented in https://coq.inria.fr/refman/addendum/type-classes.html?highlight=class#coq:cmd.class, and they don't have any advantage, so it's better to stop using them.
There are not documented in https://coq.inria.fr/refman/addendum/type-classes.html?highlight=class#coq:cmd.class, and they don't have any advantage, so it's better to stop using them.