[stm] `curr_pulseout` can be `STATIC`
[stm] `curr_pulseout` can be `STATIC`

Not used outside of PulseOut.c
adafruit/circuitpython,adafruit/circuitpython,adafruit/circuitpython,adafruit/circuitpython,adafruit/circuitpython,adafruit/circuitpython