[skip ci] Remove deprecated versions from README

Author: aaron-lane

README.md

@@ -199,7 +199,7 @@ The [project factory](https://github.com/terraform-google-modules/terraform-goog
 - [kubectl](https://github.com/kubernetes/kubernetes/releases) 1.9.x
 #### Terraform and Plugins
 - [Terraform](https://www.terraform.io/downloads.html) 0.11.x
-- [terraform-provider-google](https://github.com/terraform-providers/terraform-provider-google) v2.3, v2.6, v2.9
+- [Terraform Provider for GCP][terraform-provider-google] v2.9
 
 ### Configure a Service Account
 In order to execute this module you must have a Service Account with the