doc: correct a statement in use-case

[no ci]

docs/guide/use-case.md

@@ -118,4 +118,4 @@ $ sudo einat -i eth0 --nat44 --ports 20000-29999 --hairpin-if wg0 --internal <wg
 
 You might also want to enable NAT66 for IPv6 with `--nat66` flag if you assign private IPv6 addresses instead of public IPv6 addresses to WireGuard peers.
 
-Note if you don't specify internal source addresses with `--internal` and you are hosting TCP/UDP services on the same server, you might want to tweak external ports that `einat` uses so inbound initiated traffic towards unoccupied external ports are accepted. For example, the listening port of WireGuard service should not in range of external ports that `einat` uses(e.g. the default 20000-29999), tweak the port setting of either `einat` or WireGuard so inbound initiated traffic toward WireGuard service are accepted without filtering by `einat`.
+Note if you are hosting TCP/UDP services on same server, you might want to tweak external ports that `einat` uses so inbound initiated traffic towards unoccupied external ports are accepted. For example, the listening port of WireGuard service should not in range of external ports that `einat` uses(e.g. the default 20000-29999), tweak the port setting of either `einat` or WireGuard so inbound initiated traffic toward WireGuard service are accepted without filtering by `einat`.