[video_player_avplay] Fix getAudioTracks out of bounds issue

[xiaowei-guan]

Checked with MM team, the audio track channel range is 2 ~ 12, the AudioTrackChannelType is not suitable for use here, so return channel directly.

enum AudioTrackChannelType {
  /// The mono channel.
  mono,

  /// The stereo channel.
  stereo,

  /// The surround channel.
  surround,
}

[JSUYA]

Could you please apply this to videohole plugin as well?

[xiaowei-guan]

Could you please apply this to videohole plugin as well?

Ok, No problem, I will apply it today.

[xiaowei-guan]

#753