By THÉRÈSE MARGOLIS Out, Damned Spot! Lady Macbeth might not have been able to get rid of that “damned spot” that linked her to Duncan’s untimely demise, but now you can erase those nasty little discolorations that mar your complexion in just three days. Garnier’s new Light Complete Vitamin C Serum (sold in Mexico under the name Garnier Express Aclara