This is SO weird!
Yes, when I open your file, I can see the jaggedness too. I can see that you've rotated the photo to 2.76 degrees.
So, I tried re-rotating it. No matter what rotation I tried, it always resulted in a perfectly smooth result, exactly like it should. I tried 1 degree, 3 degrees, 3.76 degrees, even 2.77 degrees - a change of only 0.01 degree! No matter what I did, it always ended up beautifully smooth.
Not only that, when I put it back to 2.76 degrees ... perfectly smooth!!!!
Something is screwy with your Photoshop.