aggregated referees stats is off by one epoch

[ValentinTrinque]

There seems to be discrapancy between totalRefereeNotionalTakerVolume (aka PeriodVolume) and sum of epochNotionalTakerVolumes.

The observed issue is due to the condition in datanode/sqlstore/referral_sets.go which includes one more epoch than needed:

epoch_range as (select coalesce(max(id) - %d, 0) as start_epoch, coalesce(max(id), 0) as end_epoch
    from epochs
    where end_time is not null

It looks like the aggregationEpochs (%d) should be reduced by 1.

For ref: vegaprotocol/frontend-monorepo#5457