cuda module warnings

[jmackay2]

There are a few warnings when building cuda modules:

In file included from /opencv/build/modules/python_bindings_generator/pyopencv_generated_include.h:98,
                 from /opencv/modules/python/src2/cv2.cpp:11:
/opencv_contrib/modules/cudacodec/include/opencv2/cudacodec.hpp:386:20: warning: ‘class cv::cudacodec::NVSurfaceToColorConverter’ has virtual functions and accessible non-virtual destructor [-Wnon-virtual-dtor]
  386 | class CV_EXPORTS_W NVSurfaceToColorConverter {
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /opencv/build/modules/python_bindings_generator/pyopencv_generated_include.h:99:
/opencv_contrib/modules/cudafeatures2d/include/opencv2/cudafeatures2d.hpp:121:26: warning: ‘virtual void cv::cuda::DescriptorMatcher::clear()’ can be marked override [-Wsuggest-override]
  121 |     CV_WRAP virtual void clear() = 0;
      |                          ^~~~~
/opencv_contrib/modules/cudafeatures2d/include/opencv2/cudafeatures2d.hpp:125:26: warning: ‘virtual bool cv::cuda::DescriptorMatcher::empty() const’ can be marked override [-Wsuggest-override]
  125 |     CV_WRAP virtual bool empty() const = 0;
      |                          ^~~~~