Update Perforce Helix subheading to not use 'via'

doc/subscriptions/bronze_starter.md

@@ -96,7 +96,7 @@ the tiers are no longer mentioned in GitLab documentation:
     - [Trigger pull mirroring from the API](../user/project/repository/mirror/pull.md#trigger-an-update-by-using-the-api)
     - [Mirror only protected branches](../user/project/repository/mirror/index.md#mirror-only-protected-branches)
     - [Bidirectional mirroring](../user/project/repository/mirror/bidirectional.md)
-    - [Mirror with Perforce Helix via Git Fusion](../user/project/repository/mirror/bidirectional.md#mirror-with-perforce-helix-via-git-fusion)
+    - [Mirror with Perforce Helix with Git Fusion](../user/project/repository/mirror/bidirectional.md#mirror-with-perforce-helix-with-git-fusion)
 - Runners:
   - Run pipelines in the parent project [for merge requests from a forked project](../ci/pipelines/merge_request_pipelines.md#run-pipelines-in-the-parent-project-for-merge-requests-from-a-forked-project)
   - [Shared runners pipeline minutes quota](../user/admin_area/settings/continuous_integration.md#shared-runners-pipeline-minutes-quota)

doc/user/project/import/perforce.md

@@ -61,3 +61,7 @@ creating small and efficient Git pack files. So it might be a good
 idea to spend time and CPU to properly repack your repository before
 sending it for the first time to your GitLab server. See
 [this StackOverflow question](https://stackoverflow.com/questions/28720151/git-gc-aggressive-vs-git-repack/).
+
+## Related topics
+
+- [Mirror with Perforce Helix with Git Fusion](../repository/mirror/bidirectional.md#mirror-with-perforce-helix-with-git-fusion)

doc/user/project/repository/mirror/bidirectional.md

@@ -139,7 +139,7 @@ This sample has a few limitations:
 - The script circumvents the Git hook quarantine environment because the update of `$TARGET_REPO`
   is seen as a ref update, and Git displays warnings about it.
 
-## Mirror with Perforce Helix via Git Fusion **(PREMIUM)**
+## Mirror with Perforce Helix with Git Fusion **(PREMIUM)**
 
 > Moved to GitLab Premium in 13.9.