Use new go-state-types accessors (#25)

Author: arajasek

go.mod

@@ -3,8 +3,7 @@ module github.com/filecoin-project/specs-storage
 go 1.13
 
 require (
-	github.com/filecoin-project/go-state-types v0.1.3
-	github.com/filecoin-project/specs-actors/v7 v7.0.0
+	github.com/filecoin-project/go-state-types v0.1.4-0.20220511200558-7a486892661a
 	github.com/ipfs/go-cid v0.0.7
 	golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550 // indirect
 	golang.org/x/sys v0.0.0-20190826190057-c7b8b68b1456 // indirect