types: Enum: simplify the internally_discriminanted constructor

we don't actually need to enforce the discriminant codability in the
constructor.
if the conditions aren't met, the user just won't be able to operate on
the enum.

crates/types/src/compound/enumerated.rs

@@ -141,8 +141,6 @@ impl<L> Enum<(), L> {
     pub fn internally_discriminated<Variants>(v: Variants) -> Self
     where
         Variants: IntoList<List=L>,
-        L: list::Meta + Indexable<P0>,
-        list::ElementAt<P0, L>: DiscriminantCodable<<L as list::Meta>::Length>,
     {
         Enum((), v.into_list())
     }