test: remove duplicated ban test

Test the ban list is preserved through restart has been
done by both `rpc_setban` and `p2p_disconnect_ban`.
Since `p2p_disconnect_ban` does it in a more elegant
way, we can keep only it and remove the duplicated one.

test/functional/rpc_setban.py

@@ -64,20 +64,10 @@ class SetBanTests(BitcoinTestFramework):
         assert self.is_banned(node, tor_addr)
         assert not self.is_banned(node, ip_addr)
 
-        self.log.info("Test the ban list is preserved through restart")
-
-        self.restart_node(1)
-        assert self.is_banned(node, tor_addr)
-        assert not self.is_banned(node, ip_addr)
-
         node.setban(tor_addr, "remove")
         assert not self.is_banned(self.nodes[1], tor_addr)
         assert not self.is_banned(node, ip_addr)
 
-        self.restart_node(1)
-        assert not self.is_banned(node, tor_addr)
-        assert not self.is_banned(node, ip_addr)
-
         self.log.info("Test -bantime")
         self.restart_node(1, ["-bantime=1234"])
         self.nodes[1].setban("127.0.0.1", "add")