COMP: Fix -fpermissive error in StrainWindowBlockAffineTransformCommand

This commit fixes the following error reported when building
SlicerITKUltrasound extension againg Slicer 4.13 and ITK 5.3:

  In file included from /path/to/SlicerITKUltrasound-Release/ITKUltrasound/include/itkBlockMatchingStrainWindowBlockAffineTransformCommand.h:105,
                   from /path/to/SlicerITKUltrasound/GenerateDisplacementFromTimeSeries/GenerateDisplacementFromTimeSeries.cxx:38:
  /path/to/SlicerITKUltrasound-Release/ITKUltrasound/include/itkBlockMatchingStrainWindowBlockAffineTransformCommand.hxx: In instantiation of ‘void itk::BlockMatching::StrainWindowBlockAffineTransformCommand<TStrainWindowDisplacemenCalculator, TBlockAffineTransformMetricImageFilter, TStrainImageFilter>::Execute(const itk::Object*, const itk::EventObject&) [with TStrainWindowDisplacemenCalculator = itk::BlockMatching::StrainWindowDisplacementCalculator<itk::Image<float, 2>, itk::Image<itk::Vector<float, 2>, 2>, float>; TBlockAffineTransformMetricImageFilter = itk::BlockMatching::BlockAffineTransformMetricImageFilter<itk::Image<unsigned char, 2>, itk::Image<unsigned char, 2>, itk::Image<float, 2>, float>; TStrainImageFilter = itk::StrainImageFilter<itk::Image<itk::Vector<float, 2>, 2>, float, float>]’:
  /path/to/SlicerITKUltrasound-Release/ITKUltrasound/include/itkBlockMatchingStrainWindowBlockAffineTransformCommand.hxx:49:1:   required from here
  /path/to/SlicerITKUltrasound-Release/ITKUltrasound/include/itkBlockMatchingStrainWindowBlockAffineTransformCommand.hxx:73:5: error: invalid conversion from ‘const OutputImageType*’ {aka ‘const itk::Image<itk::SymmetricSecondRankTensor<float, 2>, 2>*’} to ‘itk::BlockMatching::BlockAffineTransformMetricImageFilter<itk::Image<unsigned char, 2>, itk::Image<unsigned char, 2>, itk::Image<float, 2>, float>::StrainImageType*’ {aka ‘itk::Image<itk::SymmetricSecondRankTensor<float, 2>, 2>*’} [-fpermissive]
     73 |     m_BlockAffineTransformMetricImageFilter->SetStrainImage(strainWindower->GetStrainImageFilter()->GetOutput());
        |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        |     |
        |     const OutputImageType* {aka const itk::Image<itk::SymmetricSecondRankTensor<float, 2>, 2>*}
  In file included from /path/to/Slicer-Release/ITK/Modules/IO/ImageBase/include/itkImageFileReaderException.h:22,
                   from /path/to/Slicer-Release/ITK/Modules/IO/ImageBase/include/itkImageFileReader.h:20,
                   from /path/to/SlicerITKUltrasound/GenerateDisplacementFromTimeSeries/GenerateDisplacementFromTimeSeries.cxx:19:
  /path/to/Slicer-Release/ITK/Modules/Core/Common/include/itkMacro.h:1097:33: note:   initializing argument 1 of ‘void itk::BlockMatching::BlockAffineTransformMetricImageFilter<TFixedImage, TMovingImage, TMetricImage, TStrainValueType>::SetStrainImage(itk::BlockMatching::BlockAffineTransformMetricImageFilter<TFixedImage, TMovingImage, TMetricImage, TStrainValueType>::StrainImageType*) [with TFixedImage = itk::Image<unsigned char, 2>; TMovingImage = itk::Image<unsigned char, 2>; TMetricImage = itk::Image<float, 2>; TStrainValueType = float; itk::BlockMatching::BlockAffineTransformMetricImageFilter<TFixedImage, TMovingImage, TMetricImage, TStrainValueType>::StrainImageType = itk::Image<itk::SymmetricSecondRankTensor<float, 2>, 2>]’
   1097 |   virtual void Set##name(type * _arg)                  \
  /path/to/SlicerITKUltrasound-Release/ITKUltrasound/include/itkBlockMatchingBlockAffineTransformMetricImageFilter.h:104:3: note: in expansion of macro ‘itkSetObjectMacro’
    104 |   itkSetObjectMacro(StrainImage, StrainImageType);
        |   ^~~~~~~~~~~~~~~~~

include/itkBlockMatchingStrainWindowBlockAffineTransformCommand.hxx

@@ -70,13 +70,15 @@ StrainWindowBlockAffineTransformCommand<TStrainWindowDisplacemenCalculator,
 
   if (m_UseStrainWindowStrain)
   {
-    m_BlockAffineTransformMetricImageFilter->SetStrainImage(strainWindower->GetStrainImageFilter()->GetOutput());
+    m_BlockAffineTransformMetricImageFilter->SetStrainImage(
+          const_cast<typename BlockAffineTransformMetricImageFilterType::StrainImageType *>(strainWindower->GetStrainImageFilter()->GetOutput()));
   }
   else
   {
     m_StrainImageFilter->SetInput(strainWindower->GetStrainImageFilter()->GetInput());
     m_StrainImageFilter->Update();
-    m_BlockAffineTransformMetricImageFilter->SetStrainImage(m_StrainImageFilter->GetOutput());
+    m_BlockAffineTransformMetricImageFilter->SetStrainImage(
+          const_cast<typename BlockAffineTransformMetricImageFilterType::StrainImageType *>(m_StrainImageFilter->GetOutput()));
   }
 }