development-dependency: bump andrcuns/ruby from 2.6.6-slim-10.8.6 to 2.6.6-slim-10.9 in /spec/fixture/gitlab

Can't show this merge request because the source branch dependabot-docker-spec-fixture-gitlab-andrcuns-ruby-2.6.6-slim-10.9 is missing from project georgekoltsov-multiple-projects-test-4/imported-project-ef029319134ab099. Close this merge request or update the source branch.