ci: skip unit tests on Debian testing for now #200

Job	Run time
yamllint	15s
unittest (debian:bullseye-slim)	29s
install (debian:bullseye-slim)	13s
unittest (debian:bookworm-slim)	33s
system-testing (debian:unstable-slim)	3m 43s
install (debian:bookworm-slim)	17s
unittest (debian:unstable-slim)	42s
system-testing (ubuntu:jammy)	3m 49s
install (debian:testing-slim)	17s
unittest (ubuntu:jammy)	38s
system-testing (ubuntu:mantic)	3m 49s
install (ubuntu:jammy)	14s
unittest (ubuntu:mantic)	41s
install (ubuntu:mantic)	18s
	15m 58s

Provide feedback