remove CIRCUITPY_RTC = 1 from mpconfigport.mk

Full build includes the RTC bits so don't need to enable it
in ports/broadcom/mpconfigport.mk

Author: RetiredWizard

ports/broadcom/mpconfigport.mk

@@ -15,7 +15,6 @@ CIRCUITPY_PARALLELDISPLAY = 0
 CIRCUITPY_PULSEIO = 0
 CIRCUITPY_PWMIO = 0
 CIRCUITPY_ROTARYIO = 0
-CIRCUITPY_RTC = 1
 
 CIRCUITPY_SDIOIO = 1
 CIRCUITPY_VIDEOCORE = 1