Terraform-validartor instruction should use the same version used in the foundation

[daniel-cit]

Expected Behavior

Instruction in https://github.com/GoogleCloudPlatform/terraform-example-foundation-app/tree/main/foundation-extension/4-projects#tf-validate-optional should use a fixed terraform-validator version:

To use the `validate` option of the `tf-wrapper.sh` script, please follow the [instructions](https://github.com/forseti-security/policy-library/blob/master/docs/user_guide.md#install-terraform-validator) in the **Install Terraform Validator** section and install version `2021-03-22` in your system. You will also need to rename the binary from `terraform-validator-<your-platform>` to `terraform-validator` and the `terraform-validator` binary must be in your `PATH`.

Actual Behavior

To use the `validate` option of the `tf-wrapper.sh` script, the latest version of `terraform-validator` must be [installed](https://github.com/forseti-security/policy-library/blob/master/docs/user_guide.md#how-to-use-terraform-validator) in your system and in you `PATH`.

Steps to Reproduce the Problem

1. 1. 1.

Specifications

• Version: 6645d8112fec6595d74a2c49348503f89066aa59
• Platform: Linux