Add TCP port 8443 to prerequisites for Discovery (#4748)

For sending reboot or kexec commands to discovered hosts, a TCP
connection is established from the Discovery Proxy to the discovered
host on port 8443.

Refs: https://github.com/theforeman/foreman-discovery-image/blob/9bb40867bba5c3c97dd6c76e4adc483f1babc8fa/README.md?plain=1#L28-L29
Refs: https://github.com/theforeman/smart_proxy_discovery/blob/3dc2193050f67f3a644775749aa3fa32c73b487f/settings.d/discovery.yml.example#L6
(cherry picked from commit d16a763)

Author: goarsna

guides/common/modules/con_prerequisites-for-using-discovery.adoc

@@ -15,5 +15,11 @@ For example, in the 10.1.0.0/16 network range, you can allocate the following IP
 
 ** 10.1.0.0 to 10.1.127.255 for leases.
 ** 10.1.128.0 to 10.1.255.254 for reservations.
+ifdef::satellite[]
+* For provisioning of discovered hosts using `kexec` or automatic reboot as well as reboot of discovered hosts through {ProjectWebUI}, ensure that the host and network-based firewalls are configured to allow communication from your Discovery {SmartProxy} to the discovered host on TCP port 8443.
+endif::[]
+ifndef::satellite[]
+* For provisioning of discovered hosts using `kexec` or automatic reboot as well as reboot of discovered hosts through {ProjectWebUI}, ensure that the host and network-based firewalls are configured to allow communication from your Discovery Proxy to the discovered host on TCP port 8443.
+endif::[]
 * Ensure the host or virtual machine being discovered has at least 1200 MB of memory.
 Insufficient memory can cause various random kernel panic errors because the Discovery image is extracted in memory.