Ethereum has successfully completed a major software upgrade that should make using the blockchain network ecosystem cheaper.Referred by developers as Dencun, the update lowers expenses for so-called Layer 2 networks — dozens of chains like Arbitrum, Polygon and Coinbase Global Inc.’s Base that link to Ethereum. A transaction that used to cost $1 can now be done for a cent, while a transaction that used to cost a few cents will now cost a fraction of a cent....