How do I remove myself as the SharePoint site collection administrator from having access/visibility to a folder?
You can't, this is the point of being a site collection administrator. The SCA is all seeing and is there in part to have an additional layer of privilege over those with just Full Control. If the Full Control removes all permissions from an object, the SCA can recover it.
The SCA can also see "orphaned files", those being files that have no checked in version.
As Site Collection Admin, you cannot restrict your self anything within that site collection.
But in a scenario, you dont want to access the folder. You can create new site collection and make one of the person( who need access on that folder) as Site Collection admin.