docs: update archive text (#127)

Author: ocofaigh

README.md

@@ -2,7 +2,16 @@
 
 ---
 
-:spider_web: **Archived**: This repo is no longer maintained and is archived. Please use the following public module: https://github.com/terraform-ibm-modules/terraform-ibm-observability-instances
+## Module archived
+
+:spider_web: This repo is no longer maintained and is archived. Use the following public module if you consume the module from GitHub: [terraform-ibm-observability-instances](https://github.com/terraform-ibm-modules/terraform-ibm-observability-instances)
+
+
+## Changes if you use the Hashicorp registry
+
+:exclamation: **Important:**  This module will be deleted from the Hashicorp registry on 1 August 2023. 
+
+If you  consume the module from the Hashicorp registry, use [observability-instances](https://registry.terraform.io/modules/terraform-ibm-modules/observability-instances/ibm/latest) instead.
 
 ---