Remove outdated Forseti Deployment Sample

Please remove this outdated Forseti Deployment Manager sample [here](https://github.com/GoogleCloudPlatform/deploymentmanager-samples/tree/master/community/cloud-foundation/templates/forseti). The most up to date deployment instructions can be found on our website [forsetisecurity.org](https://forsetisecurity.org/docs/latest/setup/install.html) or in our Terraform github repo [terraform-google-forseti](https://github.com/forseti-security/terraform-google-forseti)