European Union regulators are probing whether Microsoft is preventing its customers from buying security software that competes with Microsoft’s, according to a document the EU sent to at least one rival in January. It’s the latest sign of growing scrutiny from policymakers, especially in the EU, of Microsoft’s fast-growing cloud business and its practice of bundling products.Regulators from the European Commission, the agency that enforces the EU’s antitrust laws, are examining Microsoft’s Entr...