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/test/path_to_volume_id_test.pm

@@ -22,7 +22,6 @@ my $scfg = {
             'shared' => 0,
             'path' => "$storage_dir",
             'type' => 'dir',
-            'maxfiles' => 0,
             'content' => {
                 'snippets' => 1,
                 'rootdir' => 1,