No, this is a misunderstanding. You're running Linux, so the icon depends on how you installed Zotero. The official tarball, which is the only thing we can help with, includes a script that updates the .desktop file with the path to the icon. If that's what you're using, you'll need to re-run that script and get your launcher to update its cache (e.g., by restarting).
Upgrade Storage
https://www.zotero.org/support/installation#linux