Update Get-App.md

Added a note per PM.

Author: efrene

exchange/exchange-ps/exchange/Get-App.md

@@ -109,6 +109,8 @@ The Mailbox parameter specifies the identity of the mailbox where the apps are i
 
 You can't use this parameter with the Identity parameter.
 
+Note: This parameter only returns user installed and default add-ins. It doesn't return add-ins installed by admins from Integrated Apps. For more information, see [Deploy and manage Office Add-ins](https://learn.microsoft.com/microsoft-365/admin/manage/office-addins).
+
 ```yaml
 Type: MailboxIdParameter
 Parameter Sets: (All)