Allow terraform-provider-google v3.x plugin versions

* Typhoon Google Cloud is compatible with `terraform-provider-google`
v3.x releases
* No v3.x specific features are used, so v2.19+ provider versions are
still allowed, to ease migrations

docs/cl/google-cloud.md

@@ -49,7 +49,7 @@ Configure the Google Cloud provider to use your service account key, project-id,
 
 ```tf
 provider "google" {
-  version     = "2.20.0"
+  version     = "3.4.0"
   project     = "project-id"
   region      = "us-central1"
   credentials = file("~/.config/google-cloud/terraform.json")