docs/library: Update documentation of esp32's RMT.
docs/library: Update documentation of esp32's RMT.

This explains how looping now works, and removes the warning about calling
wait_done().

adafruit/circuitpython,MrSurly/micropython,kerneltask/micropython,pramasoul/micropython,henriknelson/micropython,bvernoux/micropython,bvernoux/micropython,kerneltask/micropython,henriknelson/micropython,pramasoul/micropython,MrSurly/micropython,bvernoux/micropython,selste/micropython,henriknelson/micropython,bvernoux/micropython,adafruit/circuitpython,adafruit/circuitpython,MrSurly/micropython,selste/micropython,MrSurly/micropython,selste/micropython,MrSurly/micropython,adafruit/circuitpython,kerneltask/micropython,kerneltask/micropython,kerneltask/micropython,pramasoul/micropython,bvernoux/micropython,selste/micropython,selste/micropython,adafruit/circuitpython,pramasoul/micropython,henriknelson/micropython,adafruit/circuitpython,pramasoul/micropython,henriknelson/micropython