transcode_aac: fix const return value

Fixes Trac #3613.

Signed-off-by: Timothy Gu <timothygu99@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

doc/examples/transcode_aac.c

@@ -52,7 +52,7 @@
  * @param error Error code to be converted
  * @return Corresponding error text (not thread-safe)
  */
-static char *const get_error_text(const int error)
+static const char *get_error_text(const int error)
 {
     static char error_buffer[255];
     av_strerror(error, error_buffer, sizeof(error_buffer));