Yes, simply go to your Humble download page again. If you don’t remember your download page you can use the resender -
https://www.humblebundle.com/resender - to have it re-sent to you. Then download the new copy of Slime Rancher and run that installer the same way as when you originally installed Slime Rancher. This will overwrite the old version, but your save games and preferences are stored separately, so they are safe.