The Transkribus import button leads to a 404 when the Transkribus feature is disabled

1. Turn off the transkribus feature flag in the backend.
2. Open the corpus list.
3. Under New project, click on Import a Transkribus project.
4. Page not found.
5. Cry.

The button is supposed to just not be here when the feature is not available. This confused me because I thought I could test a Transkribus import in dev when it was actually disabled.