Correct UnitarySystem error message for multi-speed coils
Forgot to correct UnitarySystem performance object idd.
Merge pull request #4541 from NREL/80880060---4534-AirloopHVACUnitarySystem-error-message-is-vague-when-UnitarySystemPerformanceHeatPumpMultispeed-is-omitted

Correct UnitarySystem error message for multi-speed coils