Use an increased modifier for posting aggregation in case node is the last node and needs more gas for additoinal logic of being the last node to submit aggregated transcript.

Basically a race condition for who will be last.

nucypher/blockchain/eth/agents.py

@@ -910,6 +910,7 @@ class CoordinatorAgent(EthereumContractAgent):
         )
         receipt = self.blockchain.send_transaction(
             contract_function=contract_function,
+            gas_estimation_multiplier=1.4,
             transacting_power=transacting_power,
             fire_and_forget=fire_and_forget,
         )