follow-up: SimpleConfig is supposed to be singleton

see cefa4762ba
and #5629

electrum/scripts/estimate_fee.py

@@ -6,10 +6,13 @@ from numbers import Number
 
 from electrum.network import filter_protocol, Network
 from electrum.util import create_and_start_event_loop, log_exceptions
+from electrum.simple_config import SimpleConfig
 
 
+config = SimpleConfig()
+
 loop, stopping_fut, loop_thread = create_and_start_event_loop()
-network = Network()
+network = Network(config)
 network.start()
 
 @log_exceptions