COMP: Use modern macro name for GetModifiableObjectMacro

Compilation error when future legacy is enabled.

In file included from ../Modules/Core/Mesh/src/itkTriangleMeshCurvatureCalculator.cxx:18:
../Modules/Core/Mesh/include/itkTriangleMeshCurvatureCalculator.h:110:3: error: use of undeclared identifier purposeful_error
  itkGetObjectMacro(GaussCurvatureData, DoubleVectorContainer);
  ^
../Modules/Core/Common/include/itkMacro.h:1128:7: note: expanded from macro itkGetObjectMacro
      purposeful_error("itkGetObjectMacro should be replaced with itkGetModifiableObjectMacro.");

Modules/Core/Mesh/include/itkTriangleMeshCurvatureCalculator.h

@@ -107,7 +107,7 @@ class ITK_TEMPLATE_EXPORT TriangleMeshCurvatureCalculator : public Object
   itkSetObjectMacro(TriangleMesh, InputMeshType);
 
   /** Get Gauss curvature. */
-  itkGetObjectMacro(GaussCurvatureData, DoubleVectorContainer);
+  itkGetModifiableObjectMacro(GaussCurvatureData, DoubleVectorContainer);
 
   /** Set the curvature type to Guass. */
   void

Modules/Core/Mesh/test/itkTriangleMeshCurvatureCalculatorTest.cxx

@@ -42,7 +42,6 @@ itkTriangleMeshCurvatureCalculatorTest(int argc, char * argv[])
   ITK_EXERCISE_BASIC_OBJECT_METHODS(curvCalculator, TriangleMeshCurvatureCalculator, Object);
 
   using DoubleVectorContainerPointer = typename CurvatureCalculatorType::DoubleVectorContainerPointer;
-  DoubleVectorContainerPointer gaussCurvatureData;
 
   // Test for empty mesh, curvature data should be null.
   TriangleMeshType::Pointer triangleMesh = TriangleMeshType::New();
@@ -69,7 +68,7 @@ itkTriangleMeshCurvatureCalculatorTest(int argc, char * argv[])
   curvCalculator->Compute();
 
   // Output should be null for empty mesh.
-  gaussCurvatureData = curvCalculator->GetGaussCurvatureData();
+  DoubleVectorContainerPointer gaussCurvatureData = curvCalculator->GetModifiableGaussCurvatureData();
   ITK_TEST_EXPECT_TRUE(gaussCurvatureData == nullptr);