[avalanche] Fix a race in abc_p2p_avalanche_contender_voting

Summary: Looking at the log while checking the isfinalrpc is racy and not redundant.

Test Plan:
  ./test/functional/test_runner.py abc_p2p_avalanche_contender_voting.py

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D17284

Author: Fabcien

test/functional/abc_p2p_avalanche_contender_voting.py

@@ -124,8 +124,7 @@ def has_finalized_tip(tip_expected):
 
         # Finalize a block so we promote the contender cache with every block
         tip = node.getbestblockhash()
-        with node.assert_debug_log([f"Avalanche finalized block {tip}"]):
-            self.wait_until(lambda: has_finalized_tip(tip))
+        self.wait_until(lambda: has_finalized_tip(tip))
         assert_equal(node.getbestblockhash(), tip)
 
         # Now trigger building the whole cache for a block