Drop no-longer applicable comments

Author: odersky

compiler/src/dotty/tools/dotc/typer/Inferencing.scala

@@ -152,8 +152,6 @@ object Inferencing {
             constraint.entry(param) match {
               case TypeBounds(lo, hi)
               if (hi frozen_<:< lo) =>
-                // if lower or upper is nonEmpty, the full bounds can't be equal, since
-                // common type params in lower and upper are eliminated through unification
                 typr.println(i"replace singleton $param := ${constraint.fullLowerBound(param)}")
                 ctx.typerState.constraint = constraint.replace(param,
                   ctx.typeComparer.approximation(param, fromBelow = true))

tests/pos/i6385.scala

@@ -12,6 +12,6 @@ object X {
 }
 
 object app extends App {
-  implicitly[Tc2[X]] // ok
-  implicitly[Tc1[X]]//(X.Tc2Instance[Tc2]) // fails
+  implicitly[Tc2[X]]
+  implicitly[Tc1[X]]
 }