message: indexer-agent: Simplify ETH balance metric typings
diff: -import { Gauge } from 'prom-client'
  import { Wallet, utils } from 'ethers'
  import { Logger, Metrics, timer } from '@graphprotocol/common-ts'
  import { indexerError, IndexerErrorCode } from '@graphprotocol/indexer-common'
  -interface EthBalanceMetrics {
  - operatorEthBalance: Gauge<string>
  -}
  -
  -const registerMetrics = (metrics: Metrics): EthBalanceMetrics => ({
  +const registerMetrics = (metrics: Metrics) => ({
  operatorEthBalance: new metrics.client.Gauge({
  name: 'indexer_agent_operator_eth_balance',
  help: 'Amount of ETH in the operatow wallet; a low amount could cause transactions to fail',
  