Remove Parent Organization types

[MattiSG]

The two types Parent Organization Privacy Policy and Parent Organization Terms of Service are not often used and are more of early choices dating from the infancy of Open Terms Archive, where we wanted to be more precise than necessary.

1. For services that completely use a parent organisation policy (such as Facebook and Instagram regarding Meta), we track directly the parent document with the simpler terms type.
2. For services that have both the simple terms type and their parent, it could now be tracked as a multi-document terms.

Only the first case has been observed in Contrib.

These types are the only ones where the writer is not the service provider itself.