Clarify/update `eth_estimateGas` default block parameter

[`eth_estimateGas`](https://besu.hyperledger.org/public-networks/reference/api#eth_estimategas) block parameter default is now `pending` instead of `latest`. May need to update block parameter description. See https://github.com/hyperledger/besu/pull/8627 for more information.