Update video_reader.cpp

Tried to build opencv with cmake and got that error:

openCV/opencv_contrib/modules/cudacodec/src/video_reader.cpp:99:14: error: extra qualification ‘{anonymous}::VideoReaderImpl::’ on member ‘set’ [-fpermissive]
   99 |         void VideoReaderImpl::set(const ColorFormat _colorFormat) CV_OVERRIDE;
      |              ^~~~~~~~~~~~~~~

Would propose do delete VideoReaderImpl:: in line 99

Author: TraubSimon

modules/cudacodec/src/video_reader.cpp

@@ -96,7 +96,7 @@ namespace
 
         bool set(const VideoReaderProps propertyId, const double propertyVal) CV_OVERRIDE;
 
-        void VideoReaderImpl::set(const ColorFormat _colorFormat) CV_OVERRIDE;
+        void set(const ColorFormat _colorFormat) CV_OVERRIDE;
 
         bool get(const VideoReaderProps propertyId, double& propertyVal) const CV_OVERRIDE;