If you like math, study math. But I don't think refreshing your math skills is the best return on investment if your goal is job hunting.

If you're looking for an ML job, the bar is mostly set by coding skillset and ML knowledge, which is a narrow area of math compared to what you might cover in a graduate math program. That said, it is important to be comfortable with the math that's relevant to ML.

Without direction you could spend a lot of time learning things that aren't going to help in your job search.