matroskadec: fix typo.

Signed-off-by: Anton Khirnov <anton@khirnov.net>

libavformat/matroskadec.c

@@ -1332,7 +1332,7 @@ static int matroska_read_header(AVFormatContext *s, AVFormatParameters *ap)
         }
         if (encodings_list->nb_elem > 1) {
             av_log(matroska->ctx, AV_LOG_ERROR,
-                   "Multiple combined encodings no supported");
+                   "Multiple combined encodings not supported");
         } else if (encodings_list->nb_elem == 1) {
             if (encodings[0].type ||
                 (encodings[0].compression.algo != MATROSKA_TRACK_ENCODING_COMP_HEADERSTRIP &&