Remove unused ci_stages FK
Ref: #436528 (closed)
What does this MR do and why?
This MR removes an unused FK on ci_stages
now that we added a FK including partition_id
in #436526 (closed).
Why are we doing this?
Necessary step in order to swap the primary key for ci_stages
and make it a composite FK.
https://docs.gitlab.com/ee/development/database/partitioning/list.html#step-5---swap-primary-key
Edited by Max Orefice