af_apad: remove unneeded av_opt_free

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

libavfilter/af_apad.c

@@ -74,8 +74,6 @@ static av_cold int init(AVFilterContext *ctx, const char *args)
         return AVERROR(EINVAL);
     }
 
-    av_opt_free(apad);
-
     return 0;
 }