Woodman’s Food Market used to be able to stock its 15 stores in Illinois and Wisconsin with the largest-size packages of Clorox Co. products, such as twin packs of 40-ounce bottles of Hidden Valley ranch salad dressing. But in 2014, Clorox decided it would only sell “large packs” to giant warehouse outlets like Costco and Sam’s Club.Claiming that this sales restriction amounted to unlawful price discrimination under Section 13(e) of the Robinson-Patman Act, Woodmans sued Clorox in federal court …