pLocalCodecParameters->channel deprecated

struct "AVCodecParameters" has no field "channels"C/C++(136)

Now have a AVChannelLayout before, in pLocalCodecParameters->ch_layout.nb_channels.

https://github.com/leandromoreira/ffmpeg-libav-tutorial/blob/f9df28a4fa01025d2e67350e368aa6da41a68ba6/README.md?plain=1#L369