DOCSP-38635 sync active source cluster (#403)

* DOCSP-38635 sync active source cluster

* Text adjustment

* Fixes per Rohan

* Fixes per Rohan

* Fixes per Rohan

* Fixes per Rohan

Co-authored-by: Rohan Sharan <[email protected]>

---------

Co-authored-by: Rohan Sharan <[email protected]>

Author: kennethdyer

source/quickstart.txt

@@ -37,6 +37,10 @@ the rest of the {+c2c-product-name+} documentation.
   meet the minimum patch :ref:`version requirements
   <c2c-server-version-compatibility>`.
 
+- The source cluster can remain active until commit because 
+  ``mongosync`` syncs writes on the source cluster for the 
+  duration of the migration until commit is called.
+
 Follow the instructions below to set up {+c2c-product-name+}, connect
 your clusters, and synchronize your data.