protomatter: Use low end of supervisor heap
protomatter: Use low end of supervisor heap

Per @tannewt, this area "sees more churn", so it's probably the right
choice here

adafruit/micropython,adafruit/circuitpython,adafruit/micropython,adafruit/circuitpython,adafruit/circuitpython,adafruit/micropython,adafruit/circuitpython,adafruit/micropython,adafruit/circuitpython,adafruit/circuitpython,adafruit/micropython