Can't Install Big Sur on Dell Precision 5510 - How do I remove the installer partition?

I tried upgrading to Big Sur from Catalina and just can't figure out how to get my Dell Precision 5510 to boot into the upgrade partition. I have decided to just stay with Catalina for now. How do I get rid of the Big Sur installer partition? FWIW, I am on OC 0.6.5. Thanks in advance.