Salsa CI: Remove default configuration file.

Instead, set ‘recipes/debian.yml@salsa-ci-team/pipeline’ as CI/CD configuration
file in the GitLab repository setting.  Per recommendation from the Salsa CI
maintainers: https://salsa.debian.org/salsa-ci-team/pipeline#debian-pipeline-for-developers .

debian/salsa-ci.yml

----
-include:
-  - https://salsa.debian.org/salsa-ci-team/pipeline/raw/master/salsa-ci.yml
-  - https://salsa.debian.org/salsa-ci-team/pipeline/raw/master/pipeline-jobs.yml