Update for Arbitrum mainnet blocktime

Looks like Arbitrum mainnet's `average_blocktime_hint` is currently set to 1.3sec: https://github.com/alloy-rs/chains/blob/0eaf7000dc3d21e47c52bfa57a72a87e28861621/src/named.rs#L357 Requesting for this to be updated to ~.25sec Recent block: https://arbiscan.io/block/170000000 Human: Jan-13-2024 09:21:33 AM +UTC Unix: 1705137693 Block from about a year ago: https://arbiscan.io/block/55000000 Human: Jan-23-2023 08:49:22 PM +UTC Unix: 1674506962 170000000 - 55000000 = 115000000 blocks 1705137693 - 1674506962 = 30630731 seconds 30630731 secs / 115000000 blocks = ~.266 seconds per block