fix name

Author: s-light

examples/displayio_layout_cartesian_lineplot.py

@@ -54,7 +54,7 @@
 print("examples/displayio_layout_cartesian_lineplot.py")
 
 # first point without a wait.
-my_plane.update_line(0, 0)
+my_plane.add_line(0, 0)
 for x, y in data:
     my_plane.add_line(x, y)
     time.sleep(0.5)