When trying to delete a repository without permissions, UI error flashes

[castelblanque]

Description:

When a user that does not have permissions to delete repos, tries to do so in a non-global repo, the UI error appears for milliseconds and then disappears. Not possible to read it.

Steps to reproduce the issue:

1. Login as a user with permissions to create a repo in a non-global namespace (e.g. default)
2. Create a non-global repo in that namespace
3. Login as a user without permissions to delete a repo but with view permissions on the namespace
4. Try to delete the repo, and confirm when prompted in the pop-up

Describe the results you received:

• Repo is not deleted -> That is correct, because user does not have permissions.
• In practice there is no UI error message. The error message flashes but for milliseconds.

Describe the results you expected:

User is shown an error message that can be seen and read.

Additional information

Perhaps the ideal situation would be that a user like this should not even be able to click on the "Delete" button if it doesn't have permissions? I mean, seeing the button disabled like the global repos buttons.

[castelblanque]

Double check first after #5121 is finished.