COMP: Mark class destructors with override

Mark class destructors with `override`.

Fixes:
```

In file included from /Users/builder/externalModules/Filtering/FFT/test/itkComplexToComplex1DFFTImageFilterTest.cxx:27:
In file included from /Users/builder/externalModules/Filtering/FFT/include/itkComplexToComplex1DFFTImageFilter.h:122:
In file included from /Users/builder/externalModules/Filtering/FFT/include/itkComplexToComplex1DFFTImageFilter.hxx:23:
[CTest: warning matched] /Users/builder/externalModules/Filtering/FFT/include/itkVnlComplexToComplex1DFFTImageFilter.h:61:11:
warning: '~VnlComplexToComplex1DFFTImageFilter' overrides a destructor but is not marked 'override' [-Winconsistent-missing-destructor-override]
  virtual ~VnlComplexToComplex1DFFTImageFilter() {}
          ^
```

and
```
In file included from /Users/builder/externalModules/Filtering/FFT/test/itkFFT1DImageFilterTest.cxx:25:
In file included from /Users/builder/externalModules/Filtering/FFT/test/itkForward1DFFTImageFilterTest.cxx:27:

In file included from /Users/builder/externalModules/Filtering/FFT/include/itkForward1DFFTImageFilter.h:101:
In file included from /Users/builder/externalModules/Filtering/FFT/include/itkForward1DFFTImageFilter.hxx:23:
[CTest: warning matched] /Users/builder/externalModules/Filtering/FFT/include/itkVnlForward1DFFTImageFilter.h:62:11:
warning: '~VnlForward1DFFTImageFilter' overrides a destructor but is not marked 'override' [-Winconsistent-missing-destructor-override]
  virtual ~VnlForward1DFFTImageFilter() {}
          ^
```

raised for example at:
https://open.cdash.org/viewBuildError.php?type=1&onlydeltap&buildid=7512728

Author: jhlegarreta

Modules/Filtering/FFT/include/itkVnlComplexToComplex1DFFTImageFilter.h

@@ -58,7 +58,7 @@ class ITK_TEMPLATE_EXPORT VnlComplexToComplex1DFFTImageFilter
 
 protected:
   VnlComplexToComplex1DFFTImageFilter() {}
-  virtual ~VnlComplexToComplex1DFFTImageFilter() {}
+  ~VnlComplexToComplex1DFFTImageFilter() override{};
 
   void
   GenerateData() override;

Modules/Filtering/FFT/include/itkVnlForward1DFFTImageFilter.h

@@ -59,7 +59,7 @@ class ITK_TEMPLATE_EXPORT VnlForward1DFFTImageFilter : public Forward1DFFTImageF
   GenerateData() override;
 
   VnlForward1DFFTImageFilter() {}
-  virtual ~VnlForward1DFFTImageFilter() {}
+  ~VnlForward1DFFTImageFilter() override{};
 
 private:
 };