fix: rm Signature optimism cfg

[mattsse]

I believe none of this is even reachable for deposit transactions.
for encoding, the signature is not included in deposit txs so we don't include them when calculating the payload len.

unclear why we had this

please check @clabby

[clabby]

This LGTM. Believe this was an artifact of the very first op-reth code where we were attempting to use reth types to read from the legacy DB. This shouldn't be necessary.

Tested on our op-sepolia node, and no issues there.

[mattsse]

thanks champ