This is because the QE variations of the GMOS-N e2v DD CCDs have never been calibrated (as mentioned in the details of the help page), so the step is not applicable for your data.
Although the differences betweeen these chips are not known conclusively, the previous instrument scientist made this comment in response to a similar query last year:
To my knowledge there is no need to apply the QE correction to these devices because they all originated from the same batch and have very similar QE as a function of wavelength.
I would be very interested to know if you find evidence that measuring such values for these CCDs would be helpful. But as far as I know the QE values are all similar enough that there would be no value to applying the correction.