ci: add distrotest:debian10

distro/tests/ansible-roles/obs_repos/tasks/Debian.yaml

 ---
 - name: Add upstream package signing key
-  apt_key:
+  get_url:
     url: https://gitlab.labs.nic.cz/knot/knot-resolver-release/raw/master/cznic-obs.gpg.asc
-    state: present
+    dest: /etc/apt/trusted.gpg.d/cznic-obs.gpg.asc
 
 - name: Add OBS repo(s)
   apt_repository: