GCS/Input Wizard: allow skipping flight mode

The firmware supports not having a flight mode switch
and the wizard allows skipping it. However, because the
default number of flight modes is 3 this creates an
invalid ManualControlSetting and prevents the rest of
the calibration procedure.
Merge pull request #1397 from peabody124/wizard_skip_flightmode

GCS/Input Wizard: allow skipping flight mode