test: Remove redundant sync_with_ping after add_p2p_connection

Also replace the two-line (send_message + sync_with_ping) with the one-line send_and_ping

test/functional/p2p_invalid_messages.py

@@ -140,7 +140,6 @@ class InvalidMessagesTest(BitcoinTestFramework):
 
         # Node is still up.
         conn = node.add_p2p_connection(P2PDataStore())
-        conn.sync_with_ping()
 
     def test_magic_bytes(self):
         conn = self.nodes[0].add_p2p_connection(P2PDataStore())