Convert: Remove 'FULL' conversion

It is no longer used.

Source/cmOutputConverter.cxx

@@ -70,9 +70,6 @@ std::string cmOutputConverter::ConvertToRelativePath(
         this->StateSnapshot.GetDirectory().GetCurrentBinaryComponents(),
         result);
       break;
-    case FULL:
-      result = cmSystemTools::CollapseFullPath(result);
-      break;
   }
   return result;
 }

Source/cmOutputConverter.h

@@ -38,7 +38,6 @@ public:
    */
   enum RelativeRoot
   {
-    FULL,
     HOME,
     START,
     HOME_OUTPUT,