DAL/Proto: use Q instead of Z to check delegate participation in DAL
Otherwise, we might have a situation, like below, where a delegate is considered to have sufficiently participated even when it didn't attest any of the attested slots.
[18:07:58.764] not_attesting_at_all
[18:07:58.764] [RPC] GET http://127.0.0.1:56181/chains/main/blocks/head/context/delegates/tz1faswCTDciRzE4oJ9jn2Vm2dvjeyA9fUzU/dal_participation
[18:07:58.765] [RPC] RPC response: 200 OK
[18:07:58.765] [RPC] {
[18:07:58.765] [RPC] "expected_assigned_shards_per_slot": 409,
[18:07:58.765] [RPC] "delegate_attested_dal_slots": 0,
[18:07:58.765] [RPC] "total_dal_attested_slots": 1,
[18:07:58.765] [RPC] "expected_dal_rewards": "212680",
[18:07:58.765] [RPC] "sufficient_dal_participation": true,
[18:07:58.765] [RPC] "denounced": false
[18:07:58.765] [RPC] }