T8153: Use simple yml style

In order to avoid issues with scan-copyrights not dealing with !!bool in yaml files, switch to a simpler format.

This kind of issue was seen in packages that ship their own configuration in d/fill.copyright.blanks.yml, and uses the skip (boolean) option, which triggers an error an prevents the pipeline to succeed.

Failing job: https://gitlab.apertis.org/pkg/libuv1/-/jobs/1081868