Fix provider source in live end-to-end example

examples/live_end_to_end_dns_zone/main.tf

@@ -1,3 +1,11 @@
+terraform {
+  required_providers {
+    dynu = {
+      source = "dynu/dynu"
+    }
+  }
+}
+
 provider "dynu" {
   api_key = var.dynu_api_key
 }