Unneeded comment removed

git-svn-id: svn://bind10.isc.org/svn/bind10/branches/trac444@3951 e5f2f494-b856-4b98-b285-d166d9295462

src/lib/datasrc/memory_datasrc.h

@@ -25,9 +25,6 @@ class Name;
 namespace datasrc {
 
 /// A derived zone class intended to be used with the memory data source.
-///
-/// \todo Is this really needed in header file? If it is used only inside
-/// MemoryDataSrc, we could move it to .cc file and not care about the impl_.
 class MemoryZone : public Zone {
     ///
     /// \name Constructors and Destructor.