fix m4 can typo

Author: hathach

variants/feather_m4_can/variant.cpp

@@ -67,7 +67,7 @@ const PinDescription g_APinDescription[PINS_COUNT]=
   { PORTA,  6, PIO_ANALOG, (PIN_ATTR_ANALOG|PIN_ATTR_PWM_E), ADC_Channel6, TC1_CH0, TC1_CH0, EXTERNAL_INT_6 },
 
   // A6, D20 - VDiv!
-  { PORTB,  0, PIO_ANALOG, PIN_ATTR_ANALOG, ADC_Channel13, NOT_ON_PWM, NOT_ON_TIMER, EXTERNAL_INT_1 },
+  { PORTB,  0, PIO_ANALOG, PIN_ATTR_ANALOG, ADC_Channel12, NOT_ON_PWM, NOT_ON_TIMER, EXTERNAL_INT_0 },
 
 
   // 21..22 I2C pins (SDA/SCL)