utvideoenc: remove unused variable

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

libavcodec/utvideoenc.c

@@ -266,7 +266,7 @@ static void median_predict(UtvideoContext *c, uint8_t *src, uint8_t *dst, int st
                            int width, int height)
 {
     int i, j;
-    int A, B, C;
+    int A, C;
     uint8_t prev;
 
     /* First line uses left neighbour prediction */