Remove v1 attestation apis

[nflaig]

The v1 attestation apis become effectively useless after electra hard fork since they only support the phase0 format. The v2 apis are fork-aware and backward compatible so it might be fine to just remove v1 soon after the hard fork but we likely need to wait until fulu for them to be removed from the beacon-api spec.

[philknows]

Same with this, could probably tag as Fulu as we can remove it then.

[nflaig]

Same with this, could probably tag as Fulu as we can remove it then.

I am not sure how aggressive we wanna be at removing those, technically could do it in our next release right after Electra but might keep them around for another fork

[philknows]

We don't need to be aggressive with it especially if we have more important matters to put our time to. But thanks for creating the issue to track removal though.