Update how-to-prerequisites.md

https://portal.microsofticm.com/imp/v3/incidents/details/319295123/home

Current limitation on schema also includes individual Security Groups.

Author: Renato Vieira

articles/active-directory/cloud-sync/how-to-prerequisites.md

@@ -195,7 +195,7 @@ The following are known limitations:
 
 ### Scoping filter
 When using OU scoping filter
-- You can only sync up to 59 separate OUs for a given configuration. 
+- You can only sync up to 59 separate OUs or Security Groups for a given configuration. 
 - Nested OUs are supported (that is, you **can** sync an OU that has 130 nested OUs, but you **cannot** sync 60 separate OUs in the same configuration). 
 
 ### Password Hash Sync