kmk.consts: rename UnicodeModes => UnicodeMode

This brings this naming into consistency with both fellow consts in the
same file (ex. LeaderMode is singular) as well as the variables in which
the consts are usually used (usually a `Firmware.unicode_mode` attribute
in a keymap).

kmk/firmware.py

@@ -38,7 +38,7 @@ import busio
 import gc
 
 import supervisor
-from kmk.consts import LeaderMode, UnicodeModes
+from kmk.consts import LeaderMode, UnicodeMode
 from kmk.hid import USB_HID
 from kmk.internal_state import InternalState
 from kmk.matrix import MatrixScanner
@@ -53,7 +53,7 @@ class Firmware:
     col_pins = None
     diode_orientation = None
 
-    unicode_mode = UnicodeModes.NOOP
+    unicode_mode = UnicodeMode.NOOP
     tap_time = 300
     leader_mode = LeaderMode.TIMEOUT
     leader_dictionary = {}