Merge branch 'patch-32' into 'master'

Update discord_notifications.md

See merge request gitlab-org/gitlab-ce!23292

doc/user/project/integrations/discord_notifications.md

 # Discord Notifications service
 
-> [Introduced](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/22684) in GitLab 11.5.
+> [Introduced](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/22684) in GitLab 11.6.
 
 The Discord Notifications service sends event notifications from GitLab to the channel for which the webhook was created.