light: goimports -w (#21325)

Author: fjl

light/postprocess.go

@@ -25,7 +25,7 @@ import (
 	"math/big"
 	"time"
 
-	"github.com/deckarep/golang-set"
+	mapset "github.com/deckarep/golang-set"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/bitutil"
 	"github.com/ethereum/go-ethereum/core"