Via the Windows GUI
To uninstall Gurobi, open the Start Menu and type "remove" to find the "Add and remove programs" section. There you will find all installed Gurobi versions, and you can select which to uninstall.
Via the command-line
To uninstall Gurobi using the command-line, please run:
msiexec /x Gurobi-9.x.x-win64.msi
Note: You need the .msi file for the respective Gurobi version to run the command line operation. You can download this installer from Software Downloads on the Gurobi website.