Fix epics and epic issues tier badge

Fix epics and epic issues tier badge
on documentation.

doc/api/api_resources.md

@@ -103,10 +103,10 @@ The following API resources are available in the group context:
 | [Custom attributes](custom_attributes.md)                        | `/groups/:id/custom_attributes` (also available for projects and users) |
 | [Debian distributions](packages/debian_group_distributions.md)   | `/groups/:id/-/packages/debian` (also available for projects) |
 | [Deploy tokens](deploy_tokens.md)                                | `/groups/:id/deploy_tokens` (also available for projects and standalone) |
-| [Discussions](discussions.md) (threaded comments) **(ULTIMATE)** | `/groups/:id/epics/.../discussions` (also available for projects) |
-| [Epic issues](epic_issues.md) **(ULTIMATE)**                     | `/groups/:id/epics/.../issues` |
-| [Epic links](epic_links.md) **(ULTIMATE)**                       | `/groups/:id/epics/.../epics` |
-| [Epics](epics.md) **(ULTIMATE)**                                 | `/groups/:id/epics` |
+| [Discussions](discussions.md) (comments and threads)             | `/groups/:id/epics/.../discussions` (also available for projects) |
+| [Epic issues](epic_issues.md) **(PREMIUM)**                      | `/groups/:id/epics/.../issues` |
+| [Epic links](epic_links.md) **(PREMIUM)**                        | `/groups/:id/epics/.../epics` |
+| [Epics](epics.md) **(PREMIUM)**                                  | `/groups/:id/epics` |
 | [Groups](groups.md)                                              | `/groups`, `/groups/.../subgroups` |
 | [Group badges](group_badges.md)                                  | `/groups/:id/badges` |
 | [Group issue boards](group_boards.md)                            | `/groups/:id/boards` |

doc/api/discussions.md

@@ -11,13 +11,14 @@ Discussions are a set of related notes on:
 
 - Snippets
 - Issues
-- Epics **(ULTIMATE)**
+- [Epics](../user/group/epics/index.md)
 - Merge requests
 - Commits
 
-This includes system notes, which are notes about changes to the object (for example,
-when a milestone changes, a corresponding system note is added). Label notes are
-not part of this API, but recorded as separate events in [resource label events](resource_label_events.md).
+This includes [comments and threads](../user/discussions/index.md) and system notes.
+System notes are notes about changes to the object (for example, when a milestone changes).
+Label notes are not part of this API, but recorded as separate events in
+[resource label events](resource_label_events.md).
 
 ## Discussions pagination