Docs: Remove porting to go section for hooks

Through 13.2 until 13.4 there was a while where the implementation
language for the Git Hooks were important as the administrator could use
feature flags go change the behaviour to Ruby. This has since been
removed, so this section of the docs can be removed too.

doc/administration/server_hooks.md

@@ -156,22 +156,6 @@ NOTE: **Note:**
 While other environment variables can be passed to server hooks, your application should not rely on
 them as they can change.
 
-## Transition to Go
-
-> - Introduced in GitLab 13.2 using feature flags.
-> - In GitLab 13.4, `update` Ruby [implementation removed](https://gitlab.com/gitlab-org/gitaly/-/merge_requests/2501).
-> - In GitLab 13.4, `post-receive` Go implementation [made default](https://gitlab.com/gitlab-org/gitaly/-/merge_requests/2502).
-
-The following server hooks have been re-implemented in Go:
-
-- `pre-receive`, with the Go implementation used by default. To use the Ruby implementation instead,
-  [disable](feature_flags.md#enable-or-disable-the-feature) the `:gitaly_go_preceive_hook` feature
-  flag.
-- `update`, with Go implementation always used. No Ruby implementation is available.
-- `post-receive`, with the Go implementation used by default. To use the Ruby implementation
-  instead, [disable](feature_flags.md#enable-or-disable-the-feature) the
-  `:gitaly_go_postreceive_hook` feature flag.
-
 ## Custom error messages
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab-foss/-/merge_requests/5073) in GitLab 8.10.