[tests] Remove is_network_split from funtional test cases

test/functional/blockchain.py

@@ -35,12 +35,6 @@ class BlockchainTest(BitcoinTestFramework):
         self.setup_clean_chain = False
         self.num_nodes = 2
 
-    def setup_network(self, split=False):
-        self.nodes = start_nodes(self.num_nodes, self.options.tmpdir)
-        connect_nodes_bi(self.nodes, 0, 1)
-        self.is_network_split = False
-        self.sync_all()
-
     def run_test(self):
         self._test_gettxoutsetinfo()
         self._test_getblockheader()