Fix renovate gitlab include tracking for Docker template

Renovate currently tracks CI templates versions in .gitlab-ci.yml, but not other files like node-version-docker.gitlab-ci.yml.

See !52 (merged) for an example.

See the following for the applicable renovate updates:

• https://docs.renovatebot.com/modules/manager/gitlabci-include/
• https://docs.renovatebot.com/modules/manager/#file-matching
• https://docs.renovatebot.com/modules/manager/gitlabci/