gitlab-ci: remove `dependencies` from jobs

Historically, `needs` specifies the jobs which need to complete
successfully and `dependencies` specifies the jobs which provide
artifacts which should be used. Modern GitLab discourages using both as
`needs` now supports an `artifacts` key to say "depend on but do not use
artifacts", so remove `dependencies` and use `needs:artifacts` where
necessary.

See: https://docs.gitlab.com/ee/ci/yaml/#needsartifacts