Remove comment about protocols and namespace no longer relevant.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@42804 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/AST/Decl.h

@@ -78,8 +78,6 @@ public:
 
   /// IdentifierNamespace - According to C99 6.2.3, there are four namespaces,
   /// labels, tags, members and ordinary identifiers.
-  /// Objective-c protocols have their own namespace, so a protocol can have 
-  /// the same name as category, class, struct, typedef, etc.
   enum IdentifierNamespace {
     IDNS_Label,
     IDNS_Tag,