avcodec/libavcodec.v: remove obsolete exports

Forgotten cruft that should have been removed in
8f483108.
Signed-off-by: James Almer <jamrial@gmail.com>

libavcodec/libavcodec.v

 LIBAVCODEC_MAJOR {
     global:
         av*;
-        #deprecated, remove after next bump
-        audio_resample;
-        audio_resample_close;
     local:
         *;
 };