Update memdocs/configmgr/develop/reference/core/clients/manage/sms_g_system_exthistory-server-wmi-class.md

Delete extra "an"

Author: Angela Fleischmann

memdocs/configmgr/develop/reference/core/clients/manage/sms_g_system_exthistory-server-wmi-class.md

@@ -1,5 +1,5 @@
 ---
-description: Learn how to create an an abstract base class representing operating system extended history for a client computer using SMS_G_System_ExtHistory.
+description: Learn how to create an abstract base class representing operating system extended history for a client computer using SMS_G_System_ExtHistory.
 title: "SMS_G_System_ExtHistory Class"
 titleSuffix: "Configuration Manager"
 ms.date: "09/20/2016"