docs/library/pyb.rst: Update docs for pyb.usb_mode() function.
docs/library/pyb.rst: Update docs for pyb.usb_mode() function.

pozetroninc/micropython,bvernoux/micropython,selste/micropython,adafruit/circuitpython,adafruit/circuitpython,kerneltask/micropython,pozetroninc/micropython,henriknelson/micropython,adafruit/circuitpython,adafruit/circuitpython,henriknelson/micropython,bvernoux/micropython,pramasoul/micropython,trezor/micropython,selste/micropython,adafruit/circuitpython,trezor/micropython,bvernoux/micropython,pozetroninc/micropython,selste/micropython,tobbad/micropython,MrSurly/micropython,kerneltask/micropython,selste/micropython,MrSurly/micropython,MrSurly/micropython,tobbad/micropython,kerneltask/micropython,pramasoul/micropython,henriknelson/micropython,tobbad/micropython,henriknelson/micropython,kerneltask/micropython,bvernoux/micropython,bvernoux/micropython,adafruit/circuitpython,henriknelson/micropython,pramasoul/micropython,tobbad/micropython,selste/micropython,trezor/micropython,pozetroninc/micropython,tobbad/micropython,kerneltask/micropython,MrSurly/micropython,pozetroninc/micropython,MrSurly/micropython,trezor/micropython,pramasoul/micropython,pramasoul/micropython,trezor/micropython