Incorrect Documentation of Baudrate

[N-Masi]

The docstring for the RFM9x class in adafruit_rfm9x.py indicates that the default baudrate is 10MHz, but you can see in the constructor that it is 5MHz.

[jerryneedell]

Good catch! The default was changed a few times and clearly the docstring was not updated. I'll fix this next time I am making changes or feel free to submit a PR to make the change.