Fix description of -Yno-kind-polymorphism

As the flag indicates with the `no-` and the docs (https://dotty.epfl.ch/docs/reference/other-new-features/kind-polymorphism.html) say, the compiler flag disables kind polymorphism, not enables it.

Author: ybasket

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

@@ -164,7 +164,7 @@ class ScalaSettings extends Settings.SettingGroup {
       //.withPostSetHook( _ => YprofileEnabled.value = true )
 
   // Extremely experimental language features
-  val YnoKindPolymorphism: Setting[Boolean] = BooleanSetting("-Yno-kind-polymorphism", "Enable kind polymorphism (see https://dotty.epfl.ch/docs/reference/kind-polymorphism.html). Potentially unsound.")
+  val YnoKindPolymorphism: Setting[Boolean] = BooleanSetting("-Yno-kind-polymorphism", "Disable kind polymorphism (see https://dotty.epfl.ch/docs/reference/kind-polymorphism.html). Potentially unsound.")
   val YexplicitNulls: Setting[Boolean] = BooleanSetting("-Yexplicit-nulls", "Make reference types non-nullable. Nullable types can be expressed with unions: e.g. String|Null.")
   val YerasedTerms: Setting[Boolean] = BooleanSetting("-Yerased-terms", "Allows the use of erased terms.")
   val YcheckInit: Setting[Boolean] = BooleanSetting("-Ycheck-init", "Check initialization of objects")