avutil/frame: fix everythnig/everything typo

libavutil/frame.h

@@ -666,7 +666,7 @@ AVFrame *av_frame_clone(const AVFrame *src);
 void av_frame_unref(AVFrame *frame);
 
 /**
- * Move everythnig contained in src to dst and reset src.
+ * Move everything contained in src to dst and reset src.
  */
 void av_frame_move_ref(AVFrame *dst, AVFrame *src);