Remove support for elastic stack
This MR removes the elastic stack files for the cluster management template. As the kubernetes pod log feature is being removed, there is no longer a need to provide specific elastic configuration.
- Related issue: gitlab-org/gitlab#360182 (closed)
- Overall deprecation issue: gitlab-org/gitlab#346485 (closed)
- Bonus context: gitlab-org/monitor/respond#111 (comment 917441990)
- Docs MR: gitlab-org/gitlab!87310 (merged)
Edited by Sarah Yasonik