With the 19.1 update that was released yesterday, the Dimension pop-up should no longer be displayed. From the Photoshop product manager in charge of this feature:
"There is a card that pops up to tell you about Dimension. As designed, it is supposed to turn off if you click “close.” However, some logic was broken when it shipped and basically “close” doesn’t work. It defers for 24 hours and then shows again, which is not at all what should happen.
We fixed this in the new version (19.1) that we shipped today. If you upgrade your version of Photoshop, you may trigger the card once more but at that point pressing close will ensure that you never EVER see it again.
I’m sorry that you were affected by this bug for the last few months."