Correct UnitarySystem error message for multi-speed coils

   ** Severe  ** AirLoopHVAC:UnitarySystem = AIRLOOP_UNITCOOL1_OFFICES
   **   ~~~   ** ... Cooling coil object type requires valid UnitarySystemPerformance:HeatPump:Multispeed for cooling to be specified with number of speeds > 0
   **  Fatal  ** GetUnitarySystemInput: Errors found in input.  Program terminates.