update link to HID usage tables

Author: schneider42

adafruit_hid/keycode.py

@@ -33,7 +33,7 @@ class Keycode:
     """USB HID Keycode constants.
 
     This list is modeled after the names for USB keycodes defined in
-    https://www.usb.org/sites/default/files/documents/hut1_12v2.pdf#page=53.
+    https://www.usb.org/sites/default/files/hut1_21_0.pdf#page=118.
     This list does not include every single code, but does include all the keys on
     a regular PC or Mac keyboard.