Fix MCU rule for Wete (#8254)

Including the `xB` suffix prevents qmk_compiler (and thus QMK Configurator) from compiling firmware for the Wete.

Rolling this change back until we work out a long-term solution for the suffixes.

keyboards/wete/rules.mk

@@ -1,5 +1,5 @@
 # MCU name
-MCU = STM32F072xB
+MCU = STM32F072
 
 # Build Options
 #   comment out to disable the options.