In the hurdles world before Sydney McLaughlin, it took years to shave fractions of seconds off records, and winning races didn’t always mean rewriting history. This once-in-a-lifetime athlete is obliterating that mindset as quickly as she’s destroying the records she sets again and again. For the fourth time in 13 months, the 22-year-old McLaughlin set the world record. On Friday, she ran the 400-meter hurdles at world championships in 50.68 seconds. She shattered her old mark by 0.73 seconds, a ridiculous number for a race of this distance and an amount of time that, in the world before McLau…