[yield] reduce pixel threshold

src/demo/yield.c

@@ -44,8 +44,10 @@ int yield_demo(struct notcurses* nc){
   struct timespec scaled;
   const long total = vy * vx;
   // less than this, and we exit almost immediately. more than this, and we
-  // run closer to twenty seconds. 11/50 it is, then.
-  const long threshold_painted = total * 11 / 50;
+  // run closer to twenty seconds. 11/50 it is, then. pixels are different.
+  // it would be nice to hit this all with a rigor stick. yes, the 1 makes
+  // all the difference in cells v pixels. FIXME
+  const long threshold_painted = total * (10 + !notcurses_canpixel(nc)) / 50;
   const int MAXITER = 256;
   timespec_div(&demodelay, MAXITER, &scaled);
   long tfilled = 0;