opensuse: repository non-oss-debug is invalid

[val4oss]

• non-oss-debug is not a valid repository. Better to remove it, otherwise command like zypper refresh fails.

It happens when trying to add --tools-tree-repository from mkosi -f:

Repository 'non-oss-debug' is invalid.
[non-oss-debug|https://download.opensuse.org/debug/tumbleweed/repo/non-oss] Failed to retrieve new repository metadata.
History:
 - [non-oss-debug|https://download.opensuse.org/debug/tumbleweed/repo/non-oss] Repository type can't be determined.
Please check if the URIs defined for this repository are pointing to a valid repository.
Skipping repository 'non-oss-debug' because of the above error.

As soon as the repositories change, mkosi want to refresh with all Tumbleweed repositories included the invalide non-oss-debug one.