Deletes code that was no longer used by the `Artifacts` contract.
No reason to keep around dead code. The `_loadAddresses` function
is used instead.

https://github.com/ethereum-optimism/optimism/blob/f5221f4d1fae6f3da1bd4d1647e45f40e2b055c4/packages/contracts-bedrock/scripts/Artifacts.s.sol#L70