BLAINE, Minn. — Rory McIlroy was not in the listed field for next week’s Travelers Championship — the PGA Tour’s final signature event of the season. What does that have to do with anything? Well, as national golf writer Bob Harig noted on social media Friday, it makes the math difficult for McIlroy — who teed it up on Tour for just the ninth time this season at last week’s U.S. Open — to reach the 15-event minimum required of PGA Tour players g…