The only thing you should bring up to your manager is if the person is not meeting their commitments in a way that impacts you meeting your own commitments; you do want the responsibility for that to land where it should. Even then, do it in a non-accusatory way.
Beyond that, it's just plain none of your business. You don't know their circumstances; maybe they're genuinely slacking, maybe they have family issues, maybe they're having physical or mental health problems, maybe they're fighting burnout/boreout, etc. I have been in this industry long enough to see quite a few people go through bad patches in their life. Consider that, someday, it might be you struggling to recover and hoping your co-workers will give you the breathing room you need.
You also don't know what, if anything, the manager is doing to address the problem nor are you entitled to. If you want to be in the business of dealing with that kind of issue, become a manager yourself.