Fix flag description

Author: Blaisorblade

compiler/src/dotty/tools/dotc/config/ScalaSettings.scala

@@ -123,8 +123,8 @@ class ScalaSettings extends Settings.SettingGroup {
   val YprofileRunGcBetweenPhases = PhasesSetting("-Yprofile-run-gc", "Run a GC between phases - this allows heap size to be accurate at the expense of more time. Specify a list of phases, or *", "_")
       //.withPostSetHook( _ => YprofileEnabled.value = true )
 
-  // Extremely experimetnal language feature
-  val YkindPolymorphism = BooleanSetting("-Ykind-polymorphism", "Potentially unsound.")
+  // Extremely experimental language features
+  val YkindPolymorphism = BooleanSetting("-Ykind-polymorphism", "Enable kind polymorphism (see http://dotty.epfl.ch/docs/reference/kind-polymorphism.html). Potentially unsound.")
 
   /** Area-specific debug output */
   val YexplainLowlevel = BooleanSetting("-Yexplain-lowlevel", "When explaining type errors, show types at a lower level.")