Removed unused definition

Author: milessabin

compiler/src/dotty/tools/dotc/core/Definitions.scala

@@ -1038,8 +1038,6 @@ class Definitions {
   lazy val PolyFunctionClass = ctx.requiredClass("scala.PolyFunction")
   def PolyFunctionType = PolyFunctionClass.typeRef
 
-  private lazy val TupleTypes: Set[TypeRef] = TupleType.toSet
-
   /** If `cls` is a class in the scala package, its name, otherwise EmptyTypeName */
   def scalaClassName(cls: Symbol)(implicit ctx: Context): TypeName =
     if (cls.isClass && cls.owner == ScalaPackageClass) cls.asClass.name else EmptyTypeName