Revert "Mention that enum declarations are implicitly final"

This reverts commit 86fc594.

Author: eernstg

accepted/future-releases/class-modifiers/feature-specification.md

@@ -657,13 +657,6 @@ we can specify the restrictions imposed by modifiers._
 
 ### Basic restrictions
 
-With respect to compile-time errors caused by missing required class
-modifiers, every `enum` declaration is considered to have the modifier
-`final`. *An enum declaration is always subject to restrictions which are
-at least as strong as the restrictions implied by that modifier. This
-ensures that we can specify those errors without mentioning an exception
-for enum declarations in every rule.*
-
 It's a compile-time error if:
 
 *   A declaration depends directly on a `sealed` declaration from another