Convert: Remove NONE conversion

It is no longer used.

Source/cmOutputConverter.cxx

@@ -75,8 +75,6 @@ std::string cmOutputConverter::Convert(const std::string& source,
     case FULL:
       result = cmSystemTools::CollapseFullPath(result);
       break;
-    case NONE:
-      break;
   }
   return this->ConvertToOutputFormat(result, output);
 }

Source/cmOutputConverter.h

@@ -38,7 +38,6 @@ public:
    */
   enum RelativeRoot
   {
-    NONE,
     FULL,
     HOME,
     START,