Badpix from flats - averaging last 4 groups

[bhilbert4]

In badpix_from_flats, for the dead flux check, we want to average the signal in the final 4 groups of each input ramp. Instead, at the moment, the code is averaging the signal in the first 4 groups.

group4[0, :, :] = np.mean(hdu_list['SCI'].data[:, 0, :, :], axis=0)
group4[1, :, :] = np.mean(hdu_list['SCI'].data[:, 1, :, :], axis=0)
group4[2, :, :] = np.mean(hdu_list['SCI'].data[:, 2, :, :], axis=0)
group4[3, :, :] = np.mean(hdu_list['SCI'].data[:, 3, :, :], axis=0)