Update Set-ActivityAlert.md

Added 'reserved for internal' for Name parameter per Issue #1116

Author: chrisda

exchange/exchange-ps/exchange/policy-and-compliance/Set-ActivityAlert.md

@@ -217,7 +217,7 @@ Accept wildcard characters: False
 ```
 
 ### -Name
-The Name parameter specifies the unique name of the activity alert. The maximum length is 64 characters. If the value contains spaces, enclose the value in quotation marks (").
+This parameter is reserved for internal Microsoft use.
 
 ```yaml
 Type: String