fixup! Fix #9107: Restore constraints after MT reduction

Author: OlivierBlanvillain

tests/neg/9107.scala

@@ -8,7 +8,7 @@ object Test {
   ] // error
 
   def ev2[X] = implicitly[
-    (M[[t] =>> internal.MatchCase[Inv[t], Int]])  =:=
-    (M[[t] =>> internal.MatchCase[Inv[t], t]])
+    (M[[t] =>> runtime.MatchCase[Inv[t], Int]])  =:=
+    (M[[t] =>> runtime.MatchCase[Inv[t], t]])
   ] // error
 }