Revert "Serial connection default changed to debugging port"
Revert "Serial connection default changed to debugging port"

This reverts commit 586e1e9fee419518a14d1b3f496b30b164bc6a33.

The "virtual COM port" appears to be causing some issues:
* It doesn't handle large inputs (e.g., image upload) on the zero pro
  and the M0-pro.
* Occasionally, the input "lags behind" by six bytes, though it has not
  been confirmed that the virual COM port is the source of this issue.

runtimeinc/mynewt_arduino_zero,runtimeinc/mynewt_arduino_zero,runtimeinc/mynewt_arduino_zero