lavf: update muxing doxy

Describe the new AVCodecParameters API.

libavformat/avformat.h

@@ -191,15 +191,15 @@
  *   avio_open2() or a custom one.
  * - Unless the format is of the AVFMT_NOSTREAMS type, at least one stream must
  *   be created with the avformat_new_stream() function. The caller should fill
- *   the @ref AVStream.codec "stream codec context" information, such as the
- *   codec @ref AVCodecContext.codec_type "type", @ref AVCodecContext.codec_id
+ *   the @ref AVStream.codecpar "stream codec parameters" information, such as the
+ *   codec @ref AVCodecParameters.codec_type "type", @ref AVCodecParameters.codec_id
  *   "id" and other parameters (e.g. width / height, the pixel or sample format,
  *   etc.) as known. The @ref AVStream.time_base "stream timebase" should
  *   be set to the timebase that the caller desires to use for this stream (note
  *   that the timebase actually used by the muxer can be different, as will be
  *   described later).
  * - It is advised to manually initialize only the relevant fields in
- *   AVCodecContext, rather than using @ref avcodec_copy_context() during
+ *   AVCodecParameters, rather than using @ref avcodec_parameters_copy() during
  *   remuxing: there is no guarantee that the codec context values remain valid
  *   for both input and output format contexts.
  * - The caller may fill in additional information, such as @ref