COMP: vtkDiscretizableColorTransferChart: Remove in-class initialization of non-const

This commit fixes error like this one:

```
error: ISO C++ forbids in-class initialization of non-const static member ‘rangeMoving’
```

Libs/Visualization/VTK/Core/vtkDiscretizableColorTransferChart.cpp

@@ -130,6 +130,8 @@ vtkDiscretizableColorTransferChart::vtkDiscretizableColorTransferChart()
 
   this->CompositeHiddenItem = CTK_NULLPTR;
   this->ControlPoints = CTK_NULLPTR;
+
+  this->rangeMoving = RangeMoving_NONE;
 }
 
 // ----------------------------------------------------------------------------

Libs/Visualization/VTK/Core/vtkDiscretizableColorTransferChart.h

@@ -94,7 +94,7 @@ protected:
   enum RangeMoving {
     RangeMoving_NONE, RangeMoving_MIN, RangeMoving_MAX
   };
-  RangeMoving rangeMoving = RangeMoving_NONE;
+  RangeMoving rangeMoving;
 
   double DataRange[2];
   double CurrentRange[2];