Federal health authorities have upgraded their recall of 13-ounce bags of Frito-Lay potato chips over fears that consuming the products, which may contain undeclared milk, could potentially be fatal. Last month, the Food and Drug Administration announced that Frito-Lay was voluntarily recalling a limited batch of products. “Those with an allergy or severe sensitivity to milk run the risk of a serious or life-threatening allergic reaction if they consume the recalled product,” the FDA said in a notice that was posted on Dec. 16. The federal agency issued a risk clarification this week, calling the recall a “Class 1”…..