tests: lnpeer: simplify MockNetwork: rm dead code

not needed since 9224404108

tests/test_lnpeer.py

@@ -68,7 +68,6 @@ def noop_lock():
 
 class MockNetwork:
     def __init__(self, tx_queue, *, config: SimpleConfig):
-        self.callbacks = defaultdict(list)
         self.lnwatcher = None
         self.interface = None
         self.fee_estimates = FeeTimeEstimates()
@@ -82,10 +81,6 @@ class MockNetwork:
         self.tx_queue = tx_queue
         self._blockchain = MockBlockchain()
 
-    @property
-    def callback_lock(self):
-        return noop_lock()
-
     def get_local_height(self):
         return self.blockchain().height()