A federal judge in Pennsylvania declined to toss a complaint with breach-of-fiduciary-duty and statutory claims — including one based on the Illinois Consumer Fraud Act — against the folks who run one of Vanguard’s retirement-oriented mutual funds.The class action plaintiffs — investors in a Vanguard “retail fund” — contend they were stuck with having to pay capital gains taxes that could have easily been avoided when Vanguard lowered the investment minimum for a related “institutional fund.” Applying Delaware law on …