Remove triggerMoistureRead() call in ISR and it's trigger variable

- This was done at the very beginning when i thought to develop this
part of the program in a different way. It is unnecessary with how I
actually ended up to structure the program. - WDT should manage TWI
only, as per current developement

firmware/atmega/source/moisture.c

@@ -17,10 +17,6 @@ void sensorsInit(void) {
     PORTC &= ~sensorMask;
 }
 
-void triggerMoistureRead(void) {
-    readSensors = true;
-}
-
 static uint16_t moistureAverage(uint8_t sensorPin) {
     uint16_t sum = 0;
     for (uint8_t i = 0; i < SENSOR_READINGS; i++) {