STYLE: Add constexpr to supportSize in BSplineDeformableTransform

`SizeType::Filled(SplineOrder + 1)` can be evaluated at compile-time.

Author: N-Dekker

Modules/Core/Transform/include/itkBSplineDeformableTransform.hxx

@@ -556,7 +556,7 @@ BSplineDeformableTransform<TParametersValueType, VDimension, VSplineOrder>::Comp
   // Zero all components of jacobian
   jacobian.SetSize(SpaceDimension, this->GetNumberOfParameters());
   jacobian.Fill(0.0);
-  auto supportSize = SizeType::Filled(SplineOrder + 1);
+  constexpr auto supportSize = SizeType::Filled(SplineOrder + 1);
 
   ContinuousIndexType index =
     this->m_CoefficientImages[0]