[9.20] chg: ci: Cleanup stress test artifacts

Backport of MR !9424

Merge branch 'backport-mnowak/avoid-some-artifacts-in-stress-tests-9.20' into 'bind-9.20'

See merge request isc-projects/bind9!9428

.gitlab-ci.yml

@@ -1642,6 +1642,10 @@ shotgun:dot:
   <<: *stress_test
   artifacts:
     untracked: true
+    exclude:
+      - "output/ns4/*.dtq*"
+      - "output/ns4/large-delta-rpz*.local"
+      - "output/rpz_*"
     when: always
   only:
     - merge_requests