I've just noticed that there are not updated containers for many of the lightclient upgrades.

For example, LightClientUpdate:

https://github.com/search?q=repo%3Aethereum%2Fconsensus-specs+%22class+LightClientUpdate%22&type=code

There's only one of these defined, but the header field technically changes in each upgrade:

https://github.com/search?q=repo%3Aethereum%2Fconsensus-specs+%22def+upgrade_lc_update_to_%22&type=code

We should define updated containers for these type of situations.

For example, we would define a new Modified LightClientUpdate section here:

https://github.com/ethereum/consensus-specs/blob/master/specs/capella/light-client/sync-protocol.md#containers

It would look like:

Modified LightClientUpdate

class LightClientUpdate(Container):
    # [Modified in Capella]
    attested_header: LightClientHeader
    next_sync_committee: SyncCommittee
    next_sync_committee_branch: NextSyncCommitteeBranch
    # [Modified in Capella]
    finalized_header: LightClientHeader
    finality_branch: FinalityBranch
    sync_aggregate: SyncAggregate
    signature_slot: Slot

This is a bit explicit, but I'd rather be explicit than confusing.