fix explicit audio_index and video_index not used

The problem occurs when the mlt_service is `avformat` instead of
`avformat-novalidate` and `audio_index` or `video_index` is supplied
that is different than default but not `astream`/`vstream` properties
(legacy project) properties. In that case, the explicit `audio_index` or
`video_index` is ignored because `astream` and `vstream` are set to some
default values. In that case, the project or command line fails to play
the correct stream. TO reproduce `melt some-media-file audio_index=2`,
for example (assuming there is a second audio track at index 2).

regression in 52c5bde

src/modules/avformat/producer_avformat.c

@@ -250,16 +250,6 @@ mlt_producer producer_avformat_init(mlt_profile profile, const char *service, ch
                     mlt_producer_close(producer);
                     producer = NULL;
                 } else if (self->seekable) {
-                    mlt_properties_set_int(properties,
-                                           "astream",
-                                           relative_stream_index(self->audio_format,
-                                                                 AVMEDIA_TYPE_AUDIO,
-                                                                 self->audio_index));
-                    mlt_properties_set_int(properties,
-                                           "vstream",
-                                           relative_stream_index(self->video_format,
-                                                                 AVMEDIA_TYPE_VIDEO,
-                                                                 self->video_index));
                     // Close the file to release resources for large playlists - reopen later as needed
                     if (self->audio_format)
                         avformat_close_input(&self->audio_format);