Use github note syntax for test warning, correctly

README.md

@@ -148,7 +148,7 @@ module "egress_space" {
 ## Testing
 
 
-> [!WARN]
+> [!WARNING]
 > Tests provision resources in the real world when not using `mock_provider`! Take care that `CF_USER`/`CF_PASSWORD` are set to an account in a suitable non-production space. If other providers, such as the AWS provider, are used, ensure the same care is taken with their credentials in your shell before running `terraform test`.
 
 [Terraform tests](https://developer.hashicorp.com/terraform/language/tests) are in progress of being written. To run for any module with a `tests` directory: