Update cpx-basic-synth.py

Author: TheKitty

Circuit_Playground_Express_USB_MIDI/cpx-basic-synth.py

@@ -9,7 +9,7 @@
 
 ### copy this file to CPX as code.py
 
-### MIT License
+### MIT License.
 
 ### Copyright (c) 2019 Kevin J. Walters