Removed println's left accidentally in code base.

Author: odersky

src/dotty/tools/dotc/typer/RefChecks.scala

@@ -276,8 +276,6 @@ object RefChecks {
         !(member.owner.thisType.baseClasses exists (_ isSubClass other.owner)) &&
         !member.is(Deferred) && !other.is(Deferred) &&
         intersectionIsEmpty(member.extendedOverriddenSymbols, other.extendedOverriddenSymbols)) {
-        println(i"${member.extendedOverriddenSymbols.toList.map(_.showLocated)}%, %")
-        println(i"${other.extendedOverriddenSymbols.toList.map(_.showLocated)}%, %")
         overrideError("cannot override a concrete member without a third member that's overridden by both " +
           "(this rule is designed to prevent ``accidental overrides'')")
       } else if (other.isStable && !member.isStable) { // (1.4)