Updating the lesson 3 readme.md(virtrual kit)

[Azathoth-11]

I was trying to create a virtual circuit using the counterfit module. But I was getting module not resolved error. Specifically running the line "from counterfit_shims_grove.grove_light_sensor_v1_2 import GroveLightSensor". It can be solved by pip installing pip install counterfit-shims-grove