Merge branch '466142-namespaces-organization-id-fk' into 'master'

Add foreign key constraint to `namespaces.organization_id`

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/166855



Merged-by: Adam Hegyi <ahegyi@gitlab.com>
Approved-by: Olivier Gonzalez <ogonzalez@gitlab.com>
Approved-by: Adam Hegyi <ahegyi@gitlab.com>
Approved-by: Rutger Wessels <rwessels@gitlab.com>
Reviewed-by: Terri Chu <tchu@gitlab.com>
Reviewed-by: Abdul Wadood <awadood@gitlab.com>
Co-authored-by: Abdul Wadood <awadood@gitlab.com>