DOCSP-16038 Document how to allow c2c to accept writes again if enableUserWriteBlocking is set to true (#277)

* DOCSP-16038 Document how to allow c2c to accept writes again

* Apply suggestions from code review

Co-authored-by: jocelyn-mendez1 <[email protected]>

* DOCS-16038 updates for Ashley's feedback

---------

Co-authored-by: jocelyn-mendez1 <[email protected]>

Author: kanchana-mongodb

source/reference/api/start.txt

@@ -140,7 +140,13 @@ Request Body Parameters
        accepts writes.
 
        To reverse sync, the ``enableUserWriteBlocking`` field must be set
-       to ``true``.
+       to ``true``. To allow the source cluster to accept writes again,
+       for example after running migration tests, run the following
+       command: 
+
+       .. code-block:: shell 
+          
+          db.adminCommand( { setUserWriteBlockMode: 1, global: false } )
 
        Default value is ``false``.