docs: epilog: point "Proxmox Backup" hyperlink to pbs wiki

This changes the "Proxmox Backup" hyperlink, which is referred to throughout the
Proxmox Backup Server documentation. Following this patch, it now points to the
pbs wiki page, rather than the unpublished product page.

*Note: This change is only a temporary measure, while the product page
(https://www.proxmox.com/proxmox-backup) is in development.

Signed-off-by: Dylan Whyte <d.whyte@proxmox.com>

docs/epilog.rst

@@ -13,7 +13,7 @@
 .. _Proxmox: https://www.proxmox.com
 .. _Proxmox Community Forum: https://forum.proxmox.com
 .. _Proxmox Virtual Environment: https://www.proxmox.com/proxmox-ve
-.. _Proxmox Backup: https://www.proxmox.com/proxmox-backup
+.. _Proxmox Backup: https://pbs.proxmox.com/wiki/index.php/Main_Page  // FIXME
 .. _PBS Development List: https://lists.proxmox.com/cgi-bin/mailman/listinfo/pbs-devel
 .. _reStructuredText: https://www.sphinx-doc.org/en/master/usage/restructuredtext/index.html
 .. _Rust: https://www.rust-lang.org/