Update using_docker_images and merge_requests docs

doc/ci/docker/using_docker_images.md

@@ -327,10 +327,6 @@ means, that when starting the container without additional options, it will run
 the database's process, while Runner expects that the image will have no
 entrypoint or at least will start with a shell as its entrypoint.
 
-Previously we would need to create our own image based on the
-`super/sql:experimental` image, set the entrypoint to a shell, and then use
-it in job's configuration, e.g.:
-
 Before the new extended Docker configuration options, you would need to create
 your own image based on the `super/sql:experimental` image, set the entrypoint
 to a shell and then use it in job's configuration, like:

doc/user/project/merge_requests/index.md

@@ -162,13 +162,6 @@ have been marked as a **Work In Progress**.
 
 [Learn more about settings a merge request as "Work In Progress".](work_in_progress_merge_requests.md)
 
-## Fast-forward merge requests
-
-If you prefer a linear Git history and a way to accept merge requests without
-creating merge commits, you can configure this on a per-project basis.
-
-[Read more about fast-forward merge requests.](fast_forward_merge.md)
-
 ## Merge request approvals
 
 > Included in [GitLab Enterprise Edition Starter][products].
@@ -180,14 +173,6 @@ list of approvers that will need to approve every merge request in a project.
 
 [Read more about merge request approvals.](merge_request_approvals.md)
 
-## Semi-linear history merge requests
-
-A merge commit is created for every merge, but the branch is only merged if
-a fast-forward merge is possible. This ensures that if the merge request build
-succeeded, the target branch build will also succeed after merging.
-
-Navigate to a project's settings, select the **Merge commit with semi-linear
-history** option under **Merge Requests: Merge method** and save your changes.
 
 ## Code Quality reports