Update uninstall in solution-office-365.md

Uninstall script didn't work cause AcquireToken became async. 
I updated the script to call AcquireTokenAsync.

Author: omerhaimov

articles/azure-monitor/insights/solution-office-365.md

@@ -197,8 +197,6 @@ To enable the administrative account for the first time, you must provide admini
 
 The last step is to subscribe the application to your Log Analytics workspace. You also do this with a PowerShell script.
 
-The last step is to subscribe the application to your Log Analytics workspace. You also do this with a PowerShell script.
-
 1. Save the following script as *office365_subscription.ps1*.
 
     ```powershell
@@ -457,15 +455,17 @@ You can remove the Office 365 management solution using the process in [Remove a
     # Create Authentication Context tied to Azure AD Tenant
     $authContext = New-Object "Microsoft.IdentityModel.Clients.ActiveDirectory.AuthenticationContext" -ArgumentList $authority
     # Acquire token
-    $global:authResultARM = $authContext.AcquireToken($resourceAppIdURIARM, $clientId, $redirectUri, "Auto")
-    $authHeader = $global:authResultARM.CreateAuthorizationHeader()
+    $platformParameters = New-Object "Microsoft.IdentityModel.Clients.ActiveDirectory.PlatformParameters" -ArgumentList "Auto"
+    $global:authResultARM = $authContext.AcquireTokenAsync($resourceAppIdURIARM, $clientId, $redirectUri, $platformParameters)
+    $global:authResultARM.Wait()
+    $authHeader = $global:authResultARM.Result.CreateAuthorizationHeader()
     $authHeader
     }
     
     Function Office-UnSubscribe-Call{
     
     #----------------------------------------------------------------------------------------------------------------------------------------------
-    $authHeader = $global:authResultARM.CreateAuthorizationHeader()
+    $authHeader = $global:authResultARM.Result.CreateAuthorizationHeader()
     $ResourceName = "https://manage.office.com"
     $SubscriptionId   = $Subscription[0].Subscription.Id
     $OfficeAPIUrl = $ARMResource + 'subscriptions/' + $SubscriptionId + '/resourceGroups/' + $ResourceGroupName + '/providers/Microsoft.OperationalInsights/workspaces/' + $WorkspaceName + '/datasources/office365datasources_'  + $SubscriptionId + $OfficeTennantId + '?api-version=2015-11-01-preview'
@@ -503,6 +503,8 @@ You can remove the Office 365 management solution using the process in [Remove a
     .\office365_unsubscribe.ps1 -WorkspaceName MyWorkspace -ResourceGroupName MyResourceGroup -SubscriptionId '60b79d74-f4e4-4867-b631-yyyyyyyyyyyy' -OfficeTennantID 'ce4464f8-a172-4dcf-b675-xxxxxxxxxxxx'
     ```
 
+You will be prompted for credentials. Provide the credentials for your Log Analytics workspace.
+
 ## Data collection
 
 ### Supported agents