LOS ANGELES — “Tron: Ares” powered up the box office grid in the top spot this weekend, but Disney’s third entry in the sci-fi franchise fell short of expectations. Despite some favorable reviews — including a three-out-of-four-star one from The Associated Press — the new “Tron” film starring Jared Leto , Greta Lee and Jeff Bridges earned $33.5 million, according to Comscore estimates on Sunday. The big-budget project, reported to cost around $150 million, arrived 15 years after “Tron: Legacy”