Exclude some Kanto-/infrastructure-related repos from gitlab-rulez

The two Kanto-related repos contain tools used by the tests that are not versioned. This also adds ci-flatdeb-builder, which I had forgotten to add back when it was created.

https://phabricator.apertis.org/T8949

Signed-off-by: Ryan Gonzalez ryan.gonzalez@collabora.com