fix typos in blockmanager_test.go
fix typos in blockmanager_test.go

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