COMP: Removed unused variables causing compiler warning.

These `seedImage` and `compareTolerance` variables are only used within a code
block that is currently commented out. Alternatively, these variables could be
deleted if it is decided that the commented out code is no longer wanted.

This resolves the following compiler warnings:

/localscratch/Users/kjweimer/ITK/Modules/Remote/GrowCut/include/itkFastGrowCut.hxx:376:14: warning: unused variable ‘seedImage’ [-Wunused-variable]
  376 |   auto       seedImage = this->GetSeedImage();
      |              ^~~~~~~~~
/localscratch/Users/kjweimer/ITK/Modules/Remote/GrowCut/include/itkFastGrowCut.hxx:381:16: warning: unused variable ‘compareTolerance’ [-Wunused-variable]
  381 |   const double compareTolerance = (spacing[0] + spacing[1] + spacing[2]) / 3.0 * 0.01;
      |                ^~~~~~~~~~~~~~~~

Author: kian-weimer

include/itkFastGrowCut.hxx

@@ -372,12 +372,12 @@ void
 FastGrowCut<TInputImage, TLabelImage, TMaskImage>::GenerateData()
 {
   auto       inputImage = this->GetInput();
-  auto       seedImage = this->GetSeedImage();
+  // auto       seedImage = this->GetSeedImage();
   auto       outputImage = this->GetOutput();
   RegionType inRegion = inputImage->GetLargestPossibleRegion();
 
   SpacingType  spacing = inputImage->GetSpacing();
-  const double compareTolerance = (spacing[0] + spacing[1] + spacing[2]) / 3.0 * 0.01;
+  // const double compareTolerance = (spacing[0] + spacing[1] + spacing[2]) / 3.0 * 0.01;
 
   // Copy seedImage into the output
   RegionType region = outputImage->GetRequestedRegion();