My student published a preprint of our published paper without me as an author
As far as I know, Google Scholar is entirely automated, and so those results will likely only change if the offending paper is updated or removed.

When you say the student 'uploaded' your paper - where did they do this? On a personal website? In a repository? Regardless, your first step is probably to contact the student and ask them to add your name or take the paper down. Bear Hanlon's Razor in mind: "never assume malice if incompetence would suffice".

If the student refuses, or ignores you, then (if applicable) you might contact whoever runs the website/repository, and ask them to amend/remove the paper. You might find that the editor/publisher of the original journal article is willing to support you here, as the republication may not be compatible with the licensing agreement originally signed.

Finally, since Google results are based on measures of how 'important' a website seems to be: you can cite, reference and advertise your original paper as much as possible, to promote it in search results.