Merge pull request #12 from semaphoreci/tf/docker

Update notice about free plan

chapters/06-tutorial-semaphore.md

@@ -32,7 +32,7 @@ To get started with Semaphore:
 - Go to _[https://semaphoreci.com](https://semaphoreci.com?utm_source=ebook&utm_medium=pdf&utm_campaign=cicd-docker-kubernetes-semaphore)_ and click to sign up with your GitHub account.
 - GitHub will ask you to let Semaphore access your profile information. Allow this so that Semaphore can create an account for you.
 - Semaphore will walk you through the process of creating an organization. Since software development is a team sport, all Semaphore projects belong to an organization. Your organization will have its own domain, for example, `awesomecode.semaphoreci.com`.
-- Semaphore will ask you to choose between a time-limited free trial with unlimited capacity, a free plan, and an open-source plan. This chapter will demonstrate a workflow using Semaphore's Docker Registry, available within a free trial or a paid account. However, you can easily replace it with a free public registry like Docker Hub and implement the same workflow with an open-source account.
+- You will be asked to choose a plan. In this chapter, we’ll use the enterprise plan which features a built-in private Docker Registry. If you’re on the free or startup plan, you can use a free public registry like Docker Hub instead. The final workflow is the same.
 - Finally, you'll be greeted with a quick product tour.
 
 ### 4.4.3 Creating a Semaphore Project For The Demo Repository
@@ -138,7 +138,7 @@ Each command has its purpose:
 
 The discerning reader will note that we introduced special environment variables; these come predefined in every job[^environment]. The variables starting with `SEMAPHORE_REGISTRY_*` are used to access the private registry. Also, we’re using `SEMAPHORE_WORKFLOW_ID`, which is guaranteed to be unique for each run, to tag the image.
 
-[^docker-registry]: Semaphore's built-in Docker registry is available under a paid plan or free trial. If you're using a free or open-source plan, use an external service like Docker Hub instead. The pipeline will be slower, but the workflow will be the same.
+[^docker-registry]: Semaphore's built-in Docker registry is available under the enterprise plan. If you're using a free, open-source, or startup plan, use an external service like Docker Hub instead. The pipeline will be slower, but the workflow will be the same.
 [^environment]: The full environment reference can be found at [https://docs.semaphoreci.com/ci-cd-environment/environment-variables](https://docs.semaphoreci.com/ci-cd-environment/environment-variables/?utm_source=ebook&utm_medium=pdf&utm_campaign=cicd-docker-kubernetes-semaphore)
 
 ![Build block](./figures/05-sem-build-block-2.png){ width=95% }