Replace HLCor by fitme

[courtiol]

Change needs to happen here: https://github.com/courtiol/IsoriX/blob/f85641cd7741b6bd004fa0443af67d50d8dbd199/IsoriX/R/calibfit.R#L600C1-L607C12

which should be changed to:

      calib_fit <-
        spaMM::fitme(
          formula = stats::formula(calib_formula),
          corrMatrix = predcov,
          fixed = lambda_list,
          data = data,
          method = lik_method
        )

This should prevent some warnings.