By Jerry Bonkowski It finally will hit home Sunday. Jeff Gordon truly is retired. You’re probably wondering how I could have missed Gordon’s retirement at the end of last season. I didn’t miss it, but I admit I’ve been in a bit of denial nonetheless. Sure, Gordon missed this season’s first five races at Daytona, Atlanta, Las Vegas, Phoenix and Fontana. But no other racetrack will Gordon be missed the most than Martinsville Speedway. The half-mile bullring in southern Virginia was Gordon’s best track performance-wise, period. In 46 career Sprint Cup starts, Gordon earned nine wins, 29 top-fives, 37 top-10 finishes and…