remove: delete unused HashPlusInt function from arbos/util (#3730)

* remove: delete unused HashPlusInt function from arbos/util

* Update util.go

---------

Co-authored-by: Pepper Lebeck-Jobe <[email protected]>

Author: futreall

arbos/util/util.go

@@ -200,10 +200,6 @@ func UintToHash(val uint64) common.Hash {
 	return common.BigToHash(new(big.Int).SetUint64(val))
 }
 
-func HashPlusInt(x common.Hash, y int64) common.Hash {
-	return common.BigToHash(new(big.Int).Add(x.Big(), big.NewInt(y))) // BUGBUG: BigToHash(x) converts abs(x) to a Hash
-}
-
 func RemapL1Address(l1Addr common.Address) common.Address {
 	sumBytes := new(big.Int).Add(new(big.Int).SetBytes(l1Addr.Bytes()), AddressAliasOffset).Bytes()
 	if len(sumBytes) > 20 {