Turn tenancy validation message into English prose (#144)

Adds a period at the end of the error message.

Author: irl

variables.tf

@@ -375,6 +375,6 @@ variable "tenancy" {
   description = "Tenancy of the instance (if the instance is running in a VPC). An instance with a tenancy of 'dedicated' runs on single-tenant hardware. The 'host' tenancy is not supported for the import-instance command. Valid values are 'default', 'dedicated', and 'host'."
   validation {
     condition     = contains(["default", "dedicated", "host"], lower(var.tenancy))
-    error_message = "Tenancy field can only be one of default, dedicated, host"
+    error_message = "Tenancy field can only be one of default, dedicated, host."
   }
 }