Merge branch 'zj-mattermost-command-help-message' into 'master'

Add help section for MM commands

## What should this MR do

Check @pedroms' design for the Mattermost service screen: https://gitlab.com/gitlab-org/gitlab-ce/issues/22540

Now this has to be implemented, I've created a clean canvas for you, @lbennett, to draw on.

## Does this MR meet the acceptance criteria?

- [x] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !7558

1 files changed, 0 insertions, 7 deletions

diff --git a/app/models/project_services/mattermost_slash_commands_service.rb b/app/models/project_services/mattermost_slash_commands_service.rb
index 67902329593..33431f41dc2 100644
--- a/app/models/project_services/mattermost_slash_commands_service.rb
+++ b/app/models/project_services/mattermost_slash_commands_service.rb
@@ -19,13 +19,6 @@ class MattermostSlashCommandsService < ChatService
     'mattermost_slash_commands'
   end
 
-  def help
-    "This service allows you to use slash commands with your Mattermost installation.<br/>
-    To setup this Service you need to create a new <b>Slash commands</b> in your Mattermost integration panel.<br/>
-    <br/>
-    Create integration with URL #{service_trigger_url(self)} and enter the token below."
-  end
-
   def fields
     [
       { type: 'text', name: 'token', placeholder: '' }