Revise deprecation to use warning box

The deprecation needs to be moved from the H1 of the page, to a
WARNING box. This commit does so.

doc/user/project/integrations/hipchat.md

@@ -4,12 +4,12 @@ group: Ecosystem
 info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
 ---
 
-# Atlassian HipChat (Deprecated) **(FREE)**
+# Atlassian HipChat **(FREE)**
 
-As of [GitLab
-13.11](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/57434), the
-HipChat integration will not send any notifications to HipChat. This
-integration is also deprecated.
+WARNING:
+This feature, and the integration for it, were
+[deprecated](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/57434) in
+GitLab 13.11. The HipChat integration no longer sends any notifications to HipChat.
 
 GitLab provides a way to send HipChat notifications upon a number of events,
 such as when a user pushes code, creates a branch or tag, adds a comment, and