Fix geo-install script

What does this merge request do and why?

Fixes this error:

Anyone getting this on a fresh geo-install?

./support/tool-version-manager-exec: line 26: gdk: command not found

Right after the first make bootstrap

Closes #3080

How to set up and validate locally

1. Follow Geo easy installation but use this MR's branch: https://gitlab.com/gitlab-org/gitlab-development-kit/-/blob/main/doc/howto/geo.md#easy-installation

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, include steps to communicate to users.
• [-] Tests added for new functionality. If not, raise an issue to follow-up.
• [-] Observability added/updated (logging, metrics, tracing).
• [-] Documentation added/updated.
• [-] Announcement added for notable changes.
• [-] gdk doctor test added.