KY: KY6183 decommission

[vespertine]

As of late 2020, KY6183 (and a bunch of other unsigned 6000-series routes in Adair County) were decommissioned. I drove KY2968, and there were also no longer any KY6183 signs from there. Time to delete this very very insignificant route. Just to note: KY6177, another 6000-series route in Adair County, is still commissioned, and I'm assuming, still signed.

v.

[mapcat]

Thanks. https://github.com/TravelMapping/HighwayData/pull/6186