lavf: Remove codec_tag from dashenc and smoothstreamingenc

Currently, the tags enforced and set on the segmenter muxer level
mismatch what the mp4/ismv muxer uses (since 713efb2c).

Skip the codec_tag altogether here, to let the user (try to) set
whichever codec/tag is preferred; the individual chained muxer will
reject invalid codecs anyway.
Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/dashenc.c

@@ -1272,6 +1272,5 @@ AVOutputFormat ff_dash_muxer = {
     .write_header   = dash_write_header,
     .write_packet   = dash_write_packet,
     .write_trailer  = dash_write_trailer,
-    .codec_tag      = (const AVCodecTag* const []){ ff_mp4_obj_type, 0 },
     .priv_class     = &dash_class,
 };

libavformat/smoothstreamingenc.c

@@ -662,6 +662,5 @@ AVOutputFormat ff_smoothstreaming_muxer = {
     .write_header   = ism_write_header,
     .write_packet   = ism_write_packet,
     .write_trailer  = ism_write_trailer,
-    .codec_tag      = (const AVCodecTag* const []){ ff_mp4_obj_type, 0 },
     .priv_class     = &ism_class,
 };