Redefine broken foreign keys on p_ci_pipelines

What does this MR do and why?

Redefines the broken foreign keys on p_ci_pipelines identified in #487947 (comment 2101608662)

The next step is to create background migrations to clear the data.

If we can't get the database locks for these migrations, they can marked as successful, except for db/post_migrate/20240917114903_partition_fk_for_p_ci_builds_and_p_ci_pipelines.rb. This is a special case because the next migration(db/post_migrate/20240917115355_revert_add_fk_to_p_ci_pipelines_from_p_ci_builds.rb) depends on it and it will have to be marked as successfully executed too.

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Related to #487947 (closed)