[FIX] util/records: fix delete_unused DOCSTRING

`delete_unused`, in spite of its name, deletes records even if they are used,
provided they are not part of a foreign key with `restrict` or `set` ondelete
clause (iow: allowing for cascading foreign keys).

Author: Pirols

src/util/records.py

@@ -1098,10 +1098,13 @@ def add_ref(ref):
 
 def delete_unused(cr, *xmlids, **kwargs):
     """
-    Remove unused records.
+    Remove unrestricted records.
 
-    This function will remove records pointed by `xmlids` only if they are not referenced
-    from any table.
+    This function will remove records, pointed by `xmlids`, only if they are NOT referenced
+    from any table with `restrict` or `set` ondelete clauses.
+
+    .. warning::
+       Indirect references are not checked and can cause the util to fail.
 
     .. note::
        The records that cannot be removed are set as `noupdate=True`.