docs(firewall): remove that ufw is shipped with Debian (#26261)

<!--Delete sections as needed -->

## Description

See commit message(s).

Just fixes a small hiccup on the docs! It makes it sounds like Debian
comes with ufw but it doesn't.

> nftables is the default and recommended firewalling framework in
Debian…
> 
> It is recommended to run
[?](https://wiki.debian.org/firewalld)firewalld…
> 
> \- [Debian Wiki: nftables](https://wiki.debian.org/nftables)

Just to confirm, I also installed Debian on a VM and checked if ufw was
present, and indeed it wasn't. This was run on a fresh express Debian
install:

```txt
root@debian13-uni:/home/seth# ufw
bash: ufw: command not found
root@debian13-uni:/home/seth# 
```

- [ ] Technical review
- [x] Editorial review
- [ ] Product review

content/manuals/engine/network/packet-filtering-firewalls.md

@@ -90,9 +90,9 @@ forwarding from `ANY` zone to the `docker` zone.
 ## Docker and ufw
 
 [Uncomplicated Firewall](https://launchpad.net/ufw)
-(ufw) is a frontend that ships with Debian and Ubuntu,
-and it lets you manage firewall rules. Docker and ufw use firewall rules in
-ways that make them incompatible with each other.
+(ufw) is a frontend that ships with Ubuntu, and it lets you manage firewall
+rules. Docker and ufw use firewall rules in ways that make them incompatible
+with each other.
 
 When you publish a container's ports using Docker, traffic to and from that
 container gets diverted before it goes through the ufw firewall settings.