ui: node: system: avoid using 'Syslog'

ui: node: system: avoid using 'Syslog'

Reported in the community forum [0]. Since Proxmox VE 8/Debian 12,
rsyslog is not installed by default for new installations anymore [1].
The information gathered by the API call comes from the systemd
journal. While 'Syslog' could be interpreted as a shorthand for
"System Log", it's better to be explicit to avoid any confusion.

In addition, the systemd journal does much more than plain syslog
messages, as argued by Fabian [2].

[0]: https://forum.proxmox.com/threads/141631/post-634675
[1]: https://www.debian.org/releases/bookworm/amd64/release-notes/ch-information.en.html#changes-to-system-logging
[2]: https://lists.proxmox.com/pipermail/pve-devel/2024-February/061765.html

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
 [TL: Mention and link to Fabian's argument ]
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>