shanghai suppport for arb chains

foundry 0.2.0 throws a warning about arb chains lacking shanghai support, particularly the push0 opcode. i believe this is a false warning since new arb chains now support shanghai and the push0 opcode. also, relevant section from the [docs](https://docs.arbitrum.io/for-devs/concepts/differences-between-arbitrum-ethereum/solidity-support#differences-from-solidity-on-ethereum): > OPCODE PUSH0 | This OPCODE was added as part of ArbOS 11 and is now supported. > -- | -- >