fix dead /renter/prices api docs link
fix dead /renter/prices api docs link

NebulousLabs/Sia,NebulousLabs/Sia,MrStrong/Sia,mharkus/Sia,ChrisSchinnerl/Sia,mtlynch/Sia,mharkus/Sia,ericflo/Sia,ericflo/Sia,mtlynch/Sia,MrStrong/Sia,ChrisSchinnerl/Sia