Update app-only-auth-powershell-v2.md

Author: dariomws

exchange/docs-conceptual/app-only-auth-powershell-v2.md

@@ -137,13 +137,16 @@ You need to assign the API permission `Exchange.ManageAsApp` so the application
 
 Create a self-signed x.509 certificate using one of the following methods:
 
-- Use the [New-SelfSignedCertificate](https://docs.microsoft.com/powershell/module/pkiclient/new-selfsignedcertificate) (recommended)
+- Use the [New-SelfSignedCertificate](https://docs.microsoft.com/powershell/module/pkiclient/new-selfsignedcertificate) and [Export-PfxCertificate](https://docs.microsoft.com/powershell/module/pkiclient/export-pfxcertificate) cmdlets to request a self-signed certificate and export it to PFX. (Recommended.)
 
 - Use the [Create-SelfSignedCertificate script](https://github.com/SharePoint/PnP-Partner-Pack/blob/master/scripts/Create-SelfSignedCertificate.ps1):
 
   ```powershell
   .\Create-SelfSignedCertificate.ps1 -CommonName "MyCompanyName" -StartDate 2020-04-01 -EndDate 2022-04-01
   ```
+  
+  > [!NOTE]
+  > Note that this script generates SHA1 certificates.
 
 ## Step 4: Attach the certificate to the Azure AD application