lang: types: Add stringer information manually

This lets us get the more correct lowercase versions of type kinds in
error messages. (These match what the user would type.)

lang/types/type.go

@@ -59,13 +59,12 @@ var (
 	TypeVariant = NewType("variant")
 )
 
-//go:generate stringer -type=Kind -trimprefix=Kind -output=kind_stringer.go
-
 // The Kind represents the base type of each value.
 type Kind int // this used to be called Type
 
 // Each Kind represents a type in the language type system.
 const (
+	// NOTE: Make sure you add entries to stringer.go if you add something.
 	KindNil Kind = iota
 	KindBool
 	KindStr