Pin HTTP Router and Topology Service versions

What does this merge request do and why?

This pins the versions of the HTTP Router and Topology Service services.

That ensures that we need to have the GDK CI pass before an update of these services reaches users or the monolith CI. We can automate this process later.

By making the versions of these services deterministic, we prevent broken master incidents, or broadly all GDK environments, due to a new service version.

• See Pin service dependencies (#2398 - closed)
• Incident that sparked this: gitlab-org/quality/engineering-productivity/master-broken-incidents#12503 (comment 2482111596)+

How to set up and validate locally

1. Run GDK_SELF_UPDATE=0 gdk update
2. Run and see the expected output

   $ git -C gitlab-http-router rev-parse HEAD
   55357d4753e6ee0705e2b6206106be0c88d95cbb

3. Run and see the expected output

   $ git -C gitlab-topology-service rev-parse HEAD
   ebed35bb055c5af82f10302cf536eb9ce7db0ab3

Impacted categories

The following categories relate to this merge request:

• gdk-reliability - e.g. When a GDK action fails to complete.
• gdk-usability - e.g. Improvements or suggestions around how the GDK functions.
• gdk-performance - e.g. When a GDK action is slow or times out.

Merge request checklist

• This MR references an issue describing the change.
• This change is backward compatible. If not, please include steps to communicate to our users.
• Tests added for new functionality. If not, please raise an issue to follow-up.
• Documentation added/updated, if needed.
• Announcement added, if change is notable.
• gdk doctor test added, if needed.