Installation Documentation on Debian 12 Are Incorrect.

## Expected Behavior
I expected to at least be able to install everything as documented.

## Current Behavior
MongoDB, version 6.0, which is listed in the instructions is not supported on Debian 12.

## Possible Solution
Update the supported version MongoDB to v8.0, both in support and in documentation.

## Steps to Reproduce (for bugs)
1. Visit: https://go2docs.graylog.org/6-0/downloading_and_installing_graylog/debian_installation.htm
2. Follow instructions as written today.
3. MongoDB v6.0 cannot be installed on Debian 12
4.

## Context
OMG I am overwhelmed with sad face emotions. Just kidding. This is just a minor issue really. I do not see any problems with running Graylog v6.0 with MongoDB v8.0 (yet). I wanted to get this written before I proceed with testing.

## Your Environment

* Graylog Version: 6.0
* Java Version: Not installed yet.
* OpenSearch Version: Not installed yet.
* MongoDB Version: Not installed yet.
* Operating System: Debian 12.7.0 (ARM64)
* Browser version: Firefox (latest)