Why give up on root just because the first time didn't work? But anyway, unless you modified the recovery, the SuperSU app being installed doesn't change or hurt anything. You might just go to the Play Store and see if you can update the app. Depending on which method you used you can just uninstall it via the Application Manager in Settings or the Play Store. If it was installed as a system app then you can just disable it via the Application Manager and no harm done. If you really need to restock (you don't) then this would be a guide:
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