Remove deprecated produce block apis

[nflaig]

We can remove the v2 produce block apis in our next release after the Electra fork on Mainnet

• GET /eth/v2/validator/blocks/{slot}
• GET /eth/v1/validator/blinded_blocks/{slot}

It makes also sense to deprecate --useProduceBlockV3 CLI flag and eventually remove it in our 2.0 release.

See ethereum/beacon-APIs#466

[philknows]

Could probably tag this as a Fulu so it doesn’t look like this is outstanding for Electra

[nflaig]

Could probably tag this as a Fulu so it doesn’t look like this is outstanding for Electra

depends how we wanna categorize it, it's more of a post-electra cleanup that's why I tagged it as electra