fix(terraform): Mise à jour syntaxe disque pour provider Proxmox v2.9

Changed from nested `disks` block (v3.0 syntax) to flat `disk` block
(v2.9 syntax):
- disks { scsi { scsi0 { disk {...} } } } → disk { slot = 0, ... }
- Added explicit slot, type, and iothread parameters
- Maintains same functionality with v2.9-compatible syntax

terraform/pve3/main.tf

@@ -40,16 +40,12 @@ resource "proxmox_vm_qemu" "etcd_witness" {
     bridge = var.k3s_network_bridge
   }
 
-  disks {
-    scsi {
-      scsi0 {
-        disk {
-          size     = var.etcd_witness_config.disk_size
-          storage  = var.storage_pool
-          iothread = true
-        }
-      }
-    }
+  disk {
+    slot     = 0
+    size     = var.etcd_witness_config.disk_size
+    type     = "scsi"
+    storage  = var.storage_pool
+    iothread = 1
   }
 
   ipconfig0  = "ip=${var.etcd_witness_config.ip},gw=${var.k3s_gateway}"