Update function temp_internet

- Use a variable for usage help string

modules/proxmox_host/functions/temp_internet.fish

@@ -1,9 +1,10 @@
 function temp_internet --description "Temporarily add or remove Internet access from a VM"
     set -l action $argv[1]
     set -l vmid   $argv[2]
+    set -i usage_help "Usage: temp_internet {add|rm} <vmid> [ip/cidr] [gateway] [bridge] [model]"
 
     if test -z "$action"
-        echo "Usage: temp_internet {add|rm} <vmid> [ip/cidr] [gateway] [bridge] [model]"
+        echo "$usage_help"
         return 1
     end
 
@@ -88,7 +89,7 @@ function temp_internet --description "Temporarily add or remove Internet access
             restartvm $vmid
 
         case '*'
-            echo "Usage: temp_internet {add|rm} <vmid> [ip/cidr] [gateway] [bridge] [model]"
+            echo "$usage_help"
             return 1
     end
 end