co2_sensor: Do not reset sensor after startup
A soft reset of the SCD30 sensor, i.e. calling `SCD30.reset()` was added in commit fe023428 to force an instant update of the measurement interval after bootup. It seems, however, that the calibration value is not stored if the sensor is reset before carrying out at least one measurement after calibration. This breaks calibration with the current code, because the ESP (and then the SCD30) is reset directly after calibration.