Update tier of Reviews functionality

It's now part of Core so documentation should reflect it.

doc/user/discussions/index.md

@@ -296,9 +296,10 @@ edit existing comments. Non-team members are restricted from adding or editing c
 
 Additionally, locked issues and merge requests can not be reopened.
 
-## Merge Request Reviews **(PREMIUM)**
+## Merge Request Reviews
 
-> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/4213) in GitLab 11.4.
+> - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/4213) in [GitLab Premium](https://about.gitlab.com/pricing/) 11.4.
+> - [Moved](https://gitlab.com/gitlab-org/gitlab/-/issues/28154) to GitLab Core in 13.1.
 
 When looking at a Merge Request diff, you are able to start a review.
 This allows you to create comments inside a Merge Request that are **only visible to you** until published,
@@ -408,10 +409,7 @@ the merge request authored by the user that applied them.
 
    ![Add a suggestion into a code block tagged properly](img/make_suggestion_v12_7.png)
 
-1. Click **Comment**.
-
-   NOTE: **Note:**
-   If you're using GitLab Premium, GitLab.com Silver, and higher tiers, the thread will display [Review](#merge-request-reviews-premium) options. Click either **Start a review**, **Add comment now**, or **Add to review** to obtain the same result.
+1. Click either **Start a review** or **Add to review** to add your comment to a [review](#merge-request-reviews), or **Add comment now** to add the comment to the thread immediately.
 
    The Suggestion in the comment can be applied by the merge request author
    directly from the merge request:

doc/user/project/merge_requests/getting_started.md

@@ -67,7 +67,7 @@ Once you have created the merge request, you can also:
 - Preview continuous integration [pipelines on the merge request widget](reviewing_and_managing_merge_requests.md#pipeline-status-in-merge-requests-widgets).
 - Preview how your changes look directly on your deployed application with [Review Apps](reviewing_and_managing_merge_requests.md#live-preview-with-review-apps).
 - [Allow collaboration on merge requests across forks](allow_collaboration.md).
-- Perform a [Review](../../discussions/index.md#merge-request-reviews-premium) in order to create multiple comments on a diff and publish them once you're ready. **(PREMIUM)**
+- Perform a [Review](../../discussions/index.md#merge-request-reviews) in order to create multiple comments on a diff and publish them once you're ready.
 - Add [code suggestions](../../discussions/index.md#suggest-changes) to change the content of merge requests directly into merge request threads, and easily apply them to the codebase directly from the UI.
 - Add a time estimation and the time spent with that merge request with [Time Tracking](../time_tracking.md#time-tracking).