docs: fix artifacts folder path, according to GitLab CE 11.8.2

What does this MR do?

root@gitlab:/var/opt/gitlab/gitlab-rails/shared/artifacts/6b/86/6b86b273ff34fce19d6b804eff5a3f5747ada4eaa22f1d49c01e52ddb7875b4b
/2019_03_25/21# ls 16/
artifacts.zip
root@gitlab:/var/opt/gitlab/gitlab-rails/shared/artifacts/6b/86/6b86b273ff34fce19d6b804eff5a3f5747ada4eaa22f1d49c01e52ddb7875b4b
/2019_03_25/21# ls 17/
metadata.gz
root@gitlab:/var/opt/gitlab/gitlab-rails/shared/artifacts/6b/86/6b86b273ff34fce19d6b804eff5a3f5747ada4eaa22f1d49c01e52ddb7875b4b
/2019_03_25/21# ls 18/
job.log

job log path changed

What are the relevant issue numbers?

no

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated via this MR
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• Security reports checked/validated by reviewer