Update Azure template

- Remove Ubuntu 20.04 (LTS support ended on May 31, 2025)
- Add Ubuntu 24.04 as the default option

azure/azuredeploy.json

@@ -24,12 +24,12 @@
     "image": {
       "type": "string",
       "allowedValues": [
-        "ubuntu22.04",
-        "ubuntu20.04"
+        "ubuntu24.04",
+        "ubuntu22.04"
       ],
-      "defaultValue": "ubuntu22.04",
+      "defaultValue": "ubuntu24.04",
       "metadata": {
-        "description": "OS to use. Ubuntu 22.04 or 20.04."
+        "description": "OS to use. Ubuntu 24.04 or 22.04."
       }
     },
     "VMSize": {
@@ -60,18 +60,18 @@
     "vhdStorageType": "Standard_LRS",
     "vnetId": "[resourceId('Microsoft.Network/virtualNetworks', variables('virtualNetworkName'))]",
     "SubnetRef": "[concat(variables('vnetId'), '/subnets/', variables('subnetName'))]",
+    "ubuntu24.04": {
+      "publisher": "Canonical",
+      "offer": "0001-com-ubuntu-server-noble",
+      "sku": "24_04-lts",
+      "version": "latest"
+    },
     "ubuntu22.04": {
       "publisher": "Canonical",
       "offer": "0001-com-ubuntu-server-jammy",
       "sku": "22_04-lts",
       "version": "latest"
     },
-    "ubuntu20.04": {
-      "publisher": "Canonical",
-      "offer": "0001-com-ubuntu-server-focal",
-      "sku": "20_04-lts",
-      "version": "latest"
-    },
     "installScriptURL": "https://raw.githubusercontent.com/hwdsl2/setup-ipsec-vpn/master/azure/install.sh",
     "installCommand": "[concat('sh install.sh ', variables('quote'), parameters('preSharedKey'), variables('quote'), ' ', variables('quote'), parameters('username'), variables('quote'), ' ', variables('quote'), parameters('password'), variables('quote'))]"
   },