Revert "Allow maxzoom to 22"
Revert "Allow maxzoom to 22"

Zhao-Qi/mapbox-studio-classic,mapbox/mapbox-studio,Zhao-Qi/mapbox-studio-classic,mapbox/mapbox-studio-classic,Zhao-Qi/mapbox-studio-classic,mapbox/mapbox-studio,Zhao-Qi/mapbox-studio-classic,xrwang/mapbox-studio,xrwang/mapbox-studio,mapbox/mapbox-studio,mapbox/mapbox-studio-classic,xrwang/mapbox-studio,xrwang/mapbox-studio,xrwang/mapbox-studio,mapbox/mapbox-studio-classic,mapbox/mapbox-studio-classic,Zhao-Qi/mapbox-studio-classic,mapbox/mapbox-studio,mapbox/mapbox-studio