Revert "avformat/flvenc: Allow muxing video codecs which are not explicitly supported by the muxer"

This commit has no known use case ATM as there are no unsupported video codecs in flv and could
theoretically be use to generate broken files allthough that would be not entirely easy as
tags/codecs still get sanity checked

This reverts commit 76f4b117.

libavformat/flvenc.c

@@ -336,13 +336,6 @@ static int unsupported_codec(AVFormatContext *s,
     return AVERROR(ENOSYS);
 }
 
-static int check_video_codec_tag(int codec_tag) {
-    if (codec_tag <= 0 || codec_tag > 15) {
-        return AVERROR(ENOSYS);
-    } else
-        return 0;
-}
-
 static int flv_write_header(AVFormatContext *s)
 {
     int i;
@@ -365,7 +358,7 @@ static int flv_write_header(AVFormatContext *s)
                 return AVERROR(EINVAL);
             }
             flv->video_enc = enc;
-            if (check_video_codec_tag(enc->codec_tag) < 0)
+            if (!ff_codec_get_tag(flv_video_codec_ids, enc->codec_id))
                 return unsupported_codec(s, "Video", enc->codec_id);
 
             if (enc->codec_id == AV_CODEC_ID_MPEG4 ||
@@ -549,9 +542,7 @@ static int flv_write_packet(AVFormatContext *s, AVPacket *pkt)
     case AVMEDIA_TYPE_VIDEO:
         avio_w8(pb, FLV_TAG_TYPE_VIDEO);
 
-        flags = enc->codec_tag;
-        if (check_video_codec_tag(flags) < 0)
-            return unsupported_codec(s, "Video", enc->codec_id);
+        flags = ff_codec_get_tag(flv_video_codec_ids, enc->codec_id);
 
         flags |= pkt->flags & AV_PKT_FLAG_KEY ? FLV_FRAME_KEY : FLV_FRAME_INTER;
         break;