Add disqus redirects to moved docs

doc/ci/pipelines/index.md

 ---
+disqus_identifier: 'https://docs.gitlab.com/ee/ci/pipelines.html'
 type: reference
 ---
 

doc/ci/pipelines/job_artifacts.md

 ---
+disqus_identifier: 'https://docs.gitlab.com/ee/user/project/pipelines/job_artifacts.html'
 type: reference, howto
 ---
 

doc/ci/pipelines/schedules.md

 ---
+disqus_identifier: 'https://docs.gitlab.com/ee/user/project/pipelines/schedules.html'
 type: reference, howto
 ---
 

doc/ci/pipelines/settings.md

 ---
+disqus_identifier: 'https://docs.gitlab.com/ee/user/project/pipelines/settings.html'
 type: reference, howto
 ---