I'm a bit short for time so I'll go over what I did prior. The issue you're getting is due to the low and high not matching up on that edge enough.
If you look at your wireframe on your low and put it over your high you can see your edge doesn't follow properly.

Then when you bake you see those seams:

I did a quick retopo over the corner part and matched up the edge better (I made the top too small which is why it doesn't look right height wise, but the point was more to show the edge itself):

Now it bakes out like this:

If you actually zoom in close enough no matter how you do it there will always be a seam, it just wont be as visible from a distance as what you initially had. There are ways to hide it better but the goal is to make less visible.
You could also try using a bevel on that edge or making it something other than just a single edge going down and following it in the middle.
I also wouldn't get too caught up with seams unless they're visible enough from the viewing distance in which the object will be seen at. If an object is going to be that close to see these seams even with a perfect set up, then you should be adding more supporting edges.