config: drop 'maxfiles' parameter

The 'maxfiles' parameter has been deprecated since the addition of
'prune-backups' in the Proxmox VE 7 beta.

The setting was auto-converted when reading the storage
configuration.

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
Link: https://lore.proxmox.com/20250718125408.133376-2-f.ebner@proxmox.com

src/PVE/Storage/Plugin.pm

@@ -159,13 +159,6 @@ my $defaultData = {
             type => 'boolean',
             optional => 1,
         },
-        maxfiles => {
-            description => "Deprecated: use 'prune-backups' instead. "
-                . "Maximal number of backup files per VM. Use '0' for unlimited.",
-            type => 'integer',
-            minimum => 0,
-            optional => 1,
-        },
         'prune-backups' => get_standard_option('prune-backups'),
         'max-protected-backups' => {
             description =>