Minor pchain UTs cleanup (ava-labs#1554)

Author: abi87

vms/platformvm/blocks/builder/helpers_test.go

@@ -250,11 +250,6 @@ func defaultState(
 	if err := state.Commit(); err != nil {
 		panic(err)
 	}
-	state.SetHeight( /*height*/ 0)
-	if err := state.Commit(); err != nil {
-		panic(err)
-	}
-
 	return state
 }
 

vms/platformvm/blocks/executor/helpers_test.go

@@ -287,10 +287,6 @@ func defaultState(
 	if err := state.Commit(); err != nil {
 		panic(err)
 	}
-	state.SetHeight( /*height*/ 0)
-	if err := state.Commit(); err != nil {
-		panic(err)
-	}
 	genesisBlkID = state.GetLastAccepted()
 	return state
 }

vms/platformvm/txs/executor/helpers_test.go

@@ -240,10 +240,6 @@ func defaultState(
 	if err := state.Commit(); err != nil {
 		panic(err)
 	}
-	state.SetHeight( /*height*/ 0)
-	if err := state.Commit(); err != nil {
-		panic(err)
-	}
 	lastAcceptedID = state.GetLastAccepted()
 	return state
 }