gboards/butterstick: move steno rules config to keymap level (#16666)

keyboards/gboards/butterstick/keymaps/default/rules.mk

@@ -0,0 +1,4 @@
+STENO_ENABLE = yes
+
+OPT_DEFS += -DONLYQWERTY -DDEBUG_MATRIX
+SRC += sten.c

keyboards/gboards/butterstick/rules.mk

@@ -12,8 +12,4 @@ EXTRAKEY_ENABLE 	= yes       # Audio control and System control
 CONSOLE_ENABLE 		= yes       # Console for debug
 COMMAND_ENABLE 		= no		# Commands for debug and configuration
 NKRO_ENABLE = yes           # Enable N-Key Rollover
-STENO_ENABLE		= yes 		# Needed for chording
-
-OPT_DEFS += -DONLYQWERTY -DDEBUG_MATRIX
-SRC += sten.c
 LTO_ENABLE = yes