There are no solvents or cleaning agents to remove Gorilla Glue once it is dry.  Sanding, scraping, scratching, or chipping it off is the only way to remove cured Gorilla Glue.  If there is a larger amount of glue, you can try taking a pair of pliers and crushing and cracking the glue and then try to flake it off.  If it a smaller amount, or if you tried to wipe it off when wet and there is now a thin film of Gorilla Glue on the seat, again lightly sanding with a fine sandpaper may be the only answer; but you will need to be really careful not to damage and scratch the vinyl seat.