example: Update decoding/encoding example to the new API.

Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

doc/examples/decoding_encoding.c

@@ -453,9 +453,6 @@ int main(int argc, char **argv)
 {
     const char *filename;
 
-    /* must be called before using avcodec lib */
-    avcodec_init();
-
     /* register all the codecs */
     avcodec_register_all();