refactor: 25.04 is not an Ubuntu LTS release (#15)

* feat: 25.04 is not an Ubuntu LTS release

* doc: removed LTS from Ubuntu 25.04

builds/linux/ubuntu/25-04/linux-ubuntu.pkrvars.hcl.example

@@ -0,0 +1,40 @@
+/*
+    DESCRIPTION:
+    Ubuntu Server 25.04 LTS variables used by the Packer Plugin for Proxmox (proxmox-iso).
+*/
+
+// Guest Operating System Metadata
+vm_os_language   = "en_US"
+vm_os_keyboard   = "us"
+vm_os_timezone   = "UTC"
+vm_os_family     = "linux"
+vm_os_name       = "ubuntu"
+vm_os_version    = "25.04-lts"
+
+// Virtual Machine Guest Operating System Setting
+vm_os_type       = "l26"
+vm_cloudinit     = true
+
+// Virtual Machine Hardware Settings
+vm_bios                 = "ovmf"
+vm_cpu_count            = 1
+vm_cpu_sockets          = 1
+vm_cpu_type             = "x86-64-v3"
+vm_mem_size             = 2048
+vm_disk_type            = "virtio"
+vm_disk_size            = "32G"
+vm_disk_format          = "raw"
+vm_disk_controller_type = "virtio-scsi-pci"
+vm_network_card_model   = "virtio"
+
+// Removable Media Settings
+iso_path     = "iso"
+iso_file     = "ubuntu-25.04-live-server-amd64.iso"
+iso_checksum = "https://releases.ubuntu.com/plucky/SHA256SUMS"
+
+// Boot Settings
+vm_boot      = "order=virtio0;ide2;net0"
+vm_boot_wait = "5s"
+
+// EFI Settings
+vm_firmware_path         = "./OVMF.fd"