Remove redundant pipeline stages from the database

What does this MR do?

This MR is an attempt to remove redundant pipeline stages that we currently have in the database because of transactions races.

Does this MR meet the acceptance criteria?

• Tests added for this feature/bug
• Review
  • Has been reviewed by Backend
  • Has been reviewed by Database

What are the relevant issue numbers?

Closes gitlab-org/gitlab-ce#41769