You’ll find lactic acid (also called butyl lactate, ethyl lactate) in all sorts of things.
Pickles, bread, soy products, etc.
It’s common to be worried about it because we associate it with lactose (a sugar in dairy).
Lactic acid is made by fermenting sugars. That sugar can be lactose (from dairy), but most lactic acid comes from sucrose, beet juice, or cornstarch (source).
In general, it’s reasonable to assume that lactic acid comes from one of those sources and is vegan.
However, some lactic acid does indeed come from lactose, and would not be considered vegan.
If you want to be 100% sure that the lactic acid on a product label comes from a vegan source, you’ll have to contact the company, there’s no way around it.