The most likely cause is a front wheel bearing assembly. GM has been having a huge problem with them for many years. Due to the design, the wheel speed sensors don't generate much of a signal to start with, and in as little as 15,000 miles the wheel bearing can develop normal play that would go unnoticed on any other car brand but on yours that causes the signal to drop so low that the computer can't read it. That makes it look like that wheel is going slower than the others so the traction control kicks in to slow the other one down that it thinks is spinning.
On any other brand you replace only the wheel speed sensor when it fails. GM likes to build their cars with large assemblies to cut down on labor cost and time on the assembly line. That means you get to buy the wheel speed sensor AND the wheel bearing whenever you need either one of them.
To verify the bearing / sensor is the cause of the problem, your mechanic will perform a test drive with a scanner that lets him view live data. He will be able to see the speeds being reported by all the wheel speed sensors when the false activation occurs.