Added a new limitation regarding JSON column

Author: shriram-muthukrishnan

articles/dms/known-issues-azure-postgresql-online.md

@@ -98,6 +98,7 @@ When you try to perform an online migration from Amazon Web Service (AWS) Relati
 - The database name can't include a semicolon (;).
 - A captured table must have a primary key. If a table doesn't have a primary key, the result of DELETE and UPDATE record operations will be unpredictable.
 - Updating a primary key segment is ignored. Applying such an update will be identified by the target as an update that didn't update any rows. The result is a record written to the exceptions table.
+- If your table has a **JSON** column, any DELETE or UPDATE operations on this table can lead to a failed migration. 
 - Migration of multiple tables with the same name but a different case might cause unpredictable behavior and isn't supported. An example is the use of table1, TABLE1, and Table1.
 - Change processing of [CREATE | ALTER | DROP | TRUNCATE] table DDLs isn't supported.
 - In Database Migration Service, a single migration activity can only accommodate up to four databases.