Fix work item ancestor loading for user namespaces

What does this MR do and why?

Issue: #433155 (closed)

Fix work item ancestor loading for user namespaces

This fixes an issue where we try to load the ancestors of a work item within a user namespace project.

We tried to preload group policies for the project, however this failed as we are in a user namespace.

Changelog: fixed

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Before	After

How to set up and validate locally

1. Create an OKR on a user namespace project
2. Create a Key Results within that OKR
3. Look at the Key Result and see the GraphQL error

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.