Added missing step to transitioning squashed migrations.

docs/topics/migrations.txt

@@ -614,12 +614,13 @@ migrations it replaces and distribute this change to all running instances
 of your application, making sure that they run ``migrate`` to store the change
 in their database.
 
-After this has been done, you must then transition the squashed migration to
-a normal initial migration, by:
+You must then transition the squashed migration to a normal migration by:
 
-- Deleting all the migration files it replaces
-- Removing the ``replaces`` argument in the ``Migration`` class of the
-  squashed migration (this is how Django tells that it is a squashed migration)
+- Deleting all the migration files it replaces.
+- Updating all migrations that depend on the deleted migrations to depend on
+  the squashed migration instead.
+- Removing the ``replaces`` attribute in the ``Migration`` class of the
+  squashed migration (this is how Django tells that it is a squashed migration).
 
 .. note::
     Once you've squashed a migration, you should not then re-squash that squashed