fix coinbase handling
Description
A race condition exists if more than one miner asks for a coinbase with different values.  The first transaction will be canceled by the second one. Coinbase transactions should only ever be canceled by the validation process after confirming they have not been mined.
@@ -2528,12 +2528,6 @@ where
.output_manager_service
.get_coinbase_transaction(tx_id, reward, fees, block_height)
.await?;
-
- // Cancel existing unmined coinbase transactions for this blockheight
- self.db
- .cancel_coinbase_transaction_at_block_height(block_height)
- .await?;
-
self.db
.insert_completed_transaction(
tx_id,
