Fixed reading of battery voltage for Heltec V3.2.

[alligitor]

See my discussions with myself: https://github.com/markqvist/Reticulum/discussions/805

…Comments from Power.h:

// there are three version of V3: V3, V3.1, and V3.2
// V3 and V3.1 have a pull up on pin_ctrl and are active low
// V3.2 has a transistor and active high
// put the pin input mode and read it.  if it's high, we have V3 or V3.1
// other wise, it's a V3.2

Also, changed the min, max, float values for V3 boards. From what I can see, most are sold with a battery like this: https://www.amazon.com/dp/B0D3LMQSGL These batteries advertise a min voltage of 3 and max of 4. Float should be a tiny bit below Max.