docs: update requirements (#1068)

- Remove the hardcoded supported version
- Improve the requirements working
- Update links

README.md

@@ -7,9 +7,9 @@
 
 ## Requirements
 
-- [Terraform](https://developer.hashicorp.com/terraform/downloads)
-  - HashiCorp recommends to use the two latest terraform releases (1.8.x, 1.9.x). Our test suite validates that our provider works with these versions.
-  - This provider uses the [terraform plugin protocol version 6](https://developer.hashicorp.com/terraform/plugin/terraform-plugin-protocol#protocol-version-6), and should work with all tools (ie. Terraform & OpenTofu) that supports it.
+- [Terraform](https://developer.hashicorp.com/terraform/install) or [OpenTofu](https://opentofu.org/docs/intro/install/)
+  - Our provider tests run with Terraform or OpenTofu releases that are supported upstream.
+  - Our provider should work with any tool that supports the [terraform plugin protocol version 6](https://developer.hashicorp.com/terraform/plugin/terraform-plugin-protocol#protocol-version-6).
 - [Go](https://go.dev/doc/install) 1.21.x (to build the provider plugin)
 
 ## API Stability