Delete `POST /eth/v1/beacon/blocks`

[michaelsproul]

These endpoints are deprecated and can be removed.

https://ethereum.github.io/beacon-APIs/#/Beacon/publishBlock

With the changes to ContextDeserialize, we are treating the v1 endpoint essentially the same as the v2 endpoint, so we may as well clean things up and removed the old deprecated v1 endpoints.

We should ensure that none of our tests are using the v1 endpoint, and that they are updated to instead use v2.

[PoulavBhowmick03]

Have done this, and tested it out. Waiting for #7515 to be merged to open the PR

[michaelsproul]

Thanks, will review once I'm back online tomorrow