ADO to GitHub - ADO Work Item links

## Description

I've performed a trial run of migration from Azure DevOps Repos to GitHub and have a query around Work Item links. According to https://docs.github.com/en/migrations/using-github-enterprise-importer/migrating-from-azure-devops-to-github-enterprise-cloud/about-migrations-from-azure-devops-to-github-enterprise-cloud#data-that-is-migrated
Work items links on pull requests are migrated. This is a pretty key feature as we have many pull requests with the linked to many different work items with Azure DevOps Boards.

However when I ran the test work items ended up like this:
The pull request not found here is because ado2gh has disabled the ADO repo. But with the Work item links on PRs being migrated to me implies I should see GitHub PR links on this work item, like https://learn.microsoft.com/en-gb/azure/devops/boards/github/link-to-from-github?view=azure-devops#view-or-open-links-from-the-development-section

I've poked around a bit but cant see what I may have done wrong. Is this an issue with the migrator?

## Reproduction Steps
- Install ado2gh cli v1.8.0
- Run generate-script pointing ado2gh at an ADO project where you have at least one repo, with completed and potentially in progress PRs that have links to ADO Boards work items.
- Run the migration powershell script
- Inspect GitHub PRs migrated, they link back to ADO work items
- Inspect the ADO work item, it shows errors for development links to pull requests (referring to the disabled ADO repo) and they dont show any links to GitHub PRs.