Update CHANGELOG.md

Author: morgante

CHANGELOG.md

@@ -11,6 +11,8 @@ Extending the adopted spec, each change should have a link to its corresponding
 ## [v5.0.0] - 2019-XX-XX
 v5.0.0 is a backwards-incompatible release. Please see the [upgrading guide](./docs/upgrading_to_v5.0.md).
 
+The v5.0.0 module requires using the [2.12 version](https://github.com/terraform-providers/terraform-provider-google/blob/master/CHANGELOG.md#2120-august-01-2019) of the Google provider.
+
 ### Added
 
 * Support for Intranode Visbiility (IV) and Veritical Pod Autoscaling (VPA) beta features [#216]