EIP-7691 blob sidecar subnet computation not updated

[nflaig]

Looks like this was missed in #4023

The electra spec only states that MAX_BLOBS_PER_BLOCK_ELECTRA should be used instead of MAX_BLOBS_PER_BLOCK

consensus-specs/specs/electra/p2p-interface.md

Line 87 in e6bddd9

* Uses of `MAX_BLOBS_PER_BLOCK` in existing validations are replaced with `MAX_BLOBS_PER_BLOCK_ELECTRA`.

However in the gossip validation there is a check which uses BLOB_SIDECAR_SUBNET_COUNT but we should use BLOB_SIDECAR_SUBNET_COUNT_ELECTRA here as well

consensus-specs/specs/deneb/p2p-interface.md

Line 180 in e6bddd9

- _[REJECT]_ The sidecar is for the correct subnet -- i.e. `compute_subnet_for_blob_sidecar(blob_sidecar.index) == subnet_id`.

It might be required to update compute_subnet_for_blob_sidecar (or simply extend the note in p2p-interface.md)

consensus-specs/specs/deneb/validator.md

Line 183 in e6bddd9

def compute_subnet_for_blob_sidecar(blob_index: BlobIndex) -> SubnetID:

[ppopth]

How about opening a PR for that?

[nflaig]

How about opening a PR for that?

Can do that, was debating if a note is sufficient on p2p-interface, but updating compute_subnet_for_blob_sidecar might be better / more explicit