tests: Add missing assert_equal import to p2p_add_connections.py

Author: achow101

test/functional/p2p_add_connections.py

@@ -6,7 +6,10 @@
 
 from test_framework.p2p import P2PInterface
 from test_framework.test_framework import BitcoinTestFramework
-from test_framework.util import check_node_connections
+from test_framework.util import (
+    assert_equal,
+    check_node_connections,
+)
 
 class P2PFeelerReceiver(P2PInterface):
     def on_version(self, message):