fix: event types have changed in 0.26.0 causing typescript errors

[roderik]

      let offer = MarketplaceOffer.load(events.id(event));

the 0.24 types of 'event' are not compatible with the 0.26 types

Workaround right now is to use yarn resolutions

  "resolutions": {
    "@graphprotocol/graph-ts": "0.26.0"
  }