Add change log entry

Author: eernstg

specification/dartLangSpec.tex

@@ -56,6 +56,11 @@
 %   is concerned with an instance member with the same basename, not a
 %   static member.
 %
+% Aug 2024
+% - Use <memberDeclaration> everywhere, the distinction between class member
+%   syntax and mixin member syntax etc. was never actually introduced. The
+%   way they differ is expressed using (non-syntax) compile-time errors.
+%
 % Jun 2024
 % - Add missing references to section 'Type dynamic' at the points where the
 %   static analysis of Object member invocations is specified.