ratecontrol: Drop xvid-rc-related struct members unused after a6901b9c6

libavcodec/ratecontrol.h

@@ -79,10 +79,6 @@ typedef struct RateControlContext{
     uint64_t qscale_sum[5];
     int frame_count[5];
     int last_non_b_pict_type;
-
-    void *non_lavc_opaque;        ///< context for non lavc rc code (for example xvid)
-    float dry_run_qscale;         ///< for xvid rc
-    int last_picture_number;      ///< for xvid rc
     AVExpr * rc_eq_eval;
 }RateControlContext;