fix support_matrix.py to handle ?=
fix support_matrix.py to handle ?=

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