avformat/cinedec: fix sizeof()

Fixes CID1197047
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/cinedec.c

@@ -74,7 +74,7 @@ static int set_metadata_int(AVDictionary **dict, const char *key, int value)
 {
     if (value) {
         char buf[64];
-        snprintf(buf, sizeof(buf - 1), "%i", value);
+        snprintf(buf, sizeof(buf), "%i", value);
         buf[sizeof(buf) - 1] = 0;
         return av_dict_set(dict, key, buf, 0);
     }