hidecode221b/xps-excel-macro: Revise fitting formula based on lmfit built-in models

The fitting formula is modified to follow the lmfit built-in models, which are normalized with FWHM. In this version, the amplitude of the peak is proportional to the peak area, which does not depend on FWHM. In the previous version, the amplitude was the height of the peak, and then the peak area is based on both amplitude and FWHM in the analytical formula.