Update schema.rb from db:migrate and fix invalid index check

What does this MR do?

Rebuilds db/schema by running rake db:migrate:reset

Are there points in the code the reviewer needs to double check?

no

Why was this MR needed?

Because db/schema is invalid and missing index_for_ci_builds_retried_migration which exist in migration. It also fixes invalid usage of index_exists? which requires column name to be present (https://apidock.com/rails/v4.2.1/ActiveRecord/ConnectionAdapters/SchemaStatements/index_exists%3F)

Screenshots (if relevant)

no

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?