Work around a type alias bug in framework types

The type alias analysis is unable to detect a rare kind
of type dependency and as a result initializes type aliases
in an order that doesn't work. Adding the extra `Class`
boilerplate here accommodates the analysis.

Please merge to v6.1.1

pkgs/typed-racket-pkgs/typed-racket-more/typed/private/framework-types.rkt

@@ -472,7 +472,8 @@
                    [x (Option Integer)]
                    [y (Option Integer)]))))
 
-(define-type Frame:Register-Group<%> Frame:Basic<%>)
+(define-type Frame:Register-Group<%>
+  (Class #:implements Frame:Basic<%>))
 
 (define-type Frame:Register-Group-Mixin
   (All (r #:row)