remove remaining pypixelbuf reference

Author: dhalbert

Welcome_to_CircuitPython/code.py

@@ -10,7 +10,7 @@
 Download the bundle from circuitpython.org/libraries and copy the
 following files to your CIRCUITPY/lib folder:
 * neopixel.mpy
-* adafruit_pypixelbuf.mpy
+* adafruit_pixelbuf.mpy
 
 Once the libraries are copied, save this file as code.py to your CIRCUITPY
 drive to run it.