Update simpleio.tone() to work with nRF52840

[kattni]

At the moment, when attempting to use simpleio.tone() on the nRF52840 (Circuit Playground Bluefruit specifically), it fails with audioio not defined on line 68 in simpleio.py.

simpleio.tone() uses audioio.RawSample. CircuitPython now uses audiocore.RawSample. As well, the nRF52840 specifically uses audiopwmio.PWMAudioOut instead of audioio.AudioOut.

There is currently a check for CircuitPython 3.0 or higher in simpleio.tone() that includes 2.x backwards compatibility. My suggestion is to remove the 2.x code and then update simpleio.tone() to sort out the nRF vs the ATSAMD code. I don't know the status of audiocore in CircuitPython 4.x, so there may still need to be a version check.

Please let me know if you need any further information.