Fix tcpoly test, remove inheritance from final case class Tuple2

Author: felixmulder

tests/pos/tcpoly_bounds1.scala

@@ -1,11 +1,3 @@
-class Foo[t[x]<: Tuple2[Int, x]]
-
-//
-class MyPair[z](a: Int, b: z) extends Tuple2[Int, z](a,b)
-
-object foo extends Foo[MyPair]
-
-
 trait Monad[m[x <: Bound[x]], Bound[x], a] // TODO: variances!
 trait ListMonad[a] extends Monad[List, [X] => Any, a] // Dotty difference: Any is not a legal argument for hk type.