fix bitmap depth

.. as noted by ＠jerryneedell

Author: jepler

examples/ov7670_displayio_pico_st7789_2in.py

@@ -78,7 +78,7 @@
     if cam.height > height:
         continue
     try:
-        bitmap = Bitmap(cam.width, cam.height, 65535)
+        bitmap = Bitmap(cam.width, cam.height, 65536)
         break
     except MemoryError:
         continue