vo: clear frame repeat flag when redrawing

This makes no sense, as the flag is supposed to be used for vsync
purposes only (when literally outputting the screen again with no
changes at all), and redrawing is often used for OSD updates.

video/out/vo.c

@@ -873,6 +873,7 @@ static void do_redraw(struct vo *vo)
     if (!frame)
         frame = &dummy;
     frame->redraw = !full_redraw; // unconditionally redraw if it was dropped
+    frame->repeat = false;
     frame->still = true;
     frame->pts = 0;
     frame->duration = -1;