Leave it
If the glue is still sticky and bonded well, you can add a layer on top of it and keep going.
If the glue is old and dried, you can try to revive it with paint thinner like naphtha, but your mileage may vary.
If you used tubular tape, or the glue looks really sus, you should probably clean it and start over.
Solvents
Solvents like paint thinner or mineral spirits can loosen the glue so you can scrape it off or wipe it with a rag. Goo gone is a citrus based cleaner that works well.
Use a plastic tool to scrape the glue so you don't damage the rim. I used a plastic knife to scrape, and when it got dull, I broke off the tip to have another sharp edge.
Make sure you wipe off the solvent with isopropyl alcohol before regluing.
Heat
Use a heat gun to loosen the glue and wipe away with a rag.