Update beacon network test vectors to latest spec

[kdeme]

Test vectors did not follow yet the latest spec changes regarding OptimisticUpdate an FinalityUpdate content keys.

Also removed the slot number from them as it doesn't really make sense for most of the objects.

[acolytec3]

LGTM. I've verified that we can generate these same new content keys.

One related question, should we also update the name of the field in the content keys for the optimistic and finality updates to be signature_slot instead of optimistic_slot and finalized_slot?

[kdeme]

One related question, should we also update the name of the field in the content keys for the optimistic and finality updates to be signature_slot instead of optimistic_slot and finalized_slot?

Yeah, I had the same idea while I was adjusting the code in Fluffy. To rename it to signature_slot instead of optimistic_slot. (or attested_slot in the case we would have taken that one).
Also because I think the optimistic slot typically refers more to the attested_header.slot

[ogenev]

Maybe it is worth adding a comment of what is the expected slot number of this and the optimistic key?

[kdeme]

Could do that. Or perhaps we can introduce some metadata to be used to verify the test.