esp32: Bump version to 1.6.9.b1.
esp32: Bump version to 1.6.9.b1.

Xykon/pycom-micropython-sigfox,husigeza/pycom-micropython-sigfox,husigeza/pycom-micropython-sigfox,husigeza/pycom-micropython-sigfox,husigeza/pycom-micropython-sigfox,Xykon/pycom-micropython-sigfox,husigeza/pycom-micropython-sigfox,Xykon/pycom-micropython-sigfox,Xykon/pycom-micropython-sigfox,Xykon/pycom-micropython-sigfox