Migration 20231205143526_remove_deployments_with_degenerate.rb might fail

[johha]

Content from #3538 (comment) @ChrisMcGowan :

The migration script when it fires runs into the following error:

[2024-01-09 18:20:21+0000] Sequel::ForeignKeyConstraintViolation: PG::ForeignKeyViolation: ERROR:  update or delete on table "deployments" violates foreign key constraint "fk_deployment_processes_deployment_guid" on table "deployment_processes" (Sequel::ForeignKeyConstraintViolation)
[2024-01-09 18:20:21+0000] DETAIL:  Key (guid)=(<app guid scrubbed>) is still referenced from table "deployment_processes".

We have over 31K rows in deployments and by count over 7,500 rows marked for delete with this migration script. Going back in this repo we found the initial framework for this in this migration script from here back in 2018.

This appears to be deleting the parent record but not the child records since a "cascade" delete is not taking place.

[philippthun]

Fixed with #3596.