terraform: update stage2 provider version declaration

In commit d31f8404 we changed the
terraform provider for uptimerobot. Reflect this change in the terraform
lock file and provider version declaration.

tf-stage2/versions.tf

@@ -7,7 +7,7 @@ terraform {
       source = "mrparkers/keycloak"
     }
     uptimerobot = {
-      source = "louy/uptimerobot"
+      source = "vexxhost/uptimerobot"
     }
   }
   required_version = ">= 0.13"