When deleting translation, its relations are not deleted

This ticket covers the "step 10" from EZP-24530
You need the patch from EZP-24530

When in the Back-Office we are deleting an object translation, its relation are not also deleted.

Steps to reproduce

• Install with 2 languages
• Add a relation list to an object (for example blog_post)
• Create a new object of that class in the main translation, add a relation list
• Create a translation of this object of this object, add a relation list

Run the SQL query:

select * from ezcontentobject_link where from_contentobject_id = {object id of the newly created object};

• 2 lines are present
• Delete the second translation and run the SQL query.
• Relation list of the translation is still here and are also displayed in the backoffice