We want to increase the usage of `environments/deployments` features. And we have a ton of examples of deploying somewhere in our documentation. Most of these examples don't use the `environment` keyword. (E.g. click on a few deployment examples in https://docs.gitlab.com/ee/ci/examples/) If we add the `environment` keyword in these, more people will discover our deployment features. (we can start by grep-ing `stage: deploy` in the main repository, and fixing all these cases)