Undocumented SeparateDatabaseAndState so crash is not RB. Refs #22918

docs/ref/migration-operations.txt

@@ -250,9 +250,9 @@ are added to the migration's dependencies.
 
 Much like :class:`RunSQL`, ensure that if you change schema inside here you're
 either doing it outside the scope of the Django model system (e.g. triggers)
-or that you use :class:`SeparateDatabaseAndState` to add in operations that will
-reflect your changes to the model state - otherwise, the versioned ORM and
-the autodetector will stop working correctly.
+or that you use a custom Operation to reflect your changes to the model
+state - otherwise, the versioned ORM and the autodetector will stop
+working correctly.
 
 By default, ``RunPython`` will run its contents inside a transaction even
 on databases that do not support DDL transactions (for example, MySQL and
@@ -268,18 +268,6 @@ set ``atomic=False``.
     ``schema_editor.connection.alias``, where ``schema_editor`` is the second
     argument to your function).
 
-SeparateDatabaseAndState
-------------------------
-
-.. class:: SeparateDatabaseAndState(database_operations=None, state_operations=None)
-
-A highly specialized operation that let you mix and match the database
-(schema-changing) and state (autodetector-powering) aspects of operations.
-
-It accepts two list of operations, and when asked to apply state will use the
-state list, and when asked to apply changes to the database will use the database
-list. Do not use this operation unless you're very sure you know what you're doing.
-
 Writing your own
 ================