Update New-ServicePrincipal.md

Author: chrisda

exchange/exchange-ps/exchange/New-ServicePrincipal.md

@@ -22,6 +22,7 @@ For information about the parameter sets in the Syntax section below, see [Excha
 
 ```
 New-ServicePrincipal -AppId <String> -ObjectId <String>
+ -ServiceId <String>
  [-Confirm]
  [-DisplayName <String>]
  [-WhatIf]
@@ -86,6 +87,22 @@ Accept pipeline input: False
 Accept wildcard characters: False
 ```
 
+### -ServiceId
+This parameter is being deprecated. Use the ObjectId parameter instead.
+
+```yaml
+Type: String
+Parameter Sets: (All)
+Aliases:
+Applicable: Exchange Online, Security & Compliance, Exchange Online Protection
+
+Required: True
+Position: Named
+Default value: None
+Accept pipeline input: False
+Accept wildcard characters: False
+```
+
 ### -Confirm
 The Confirm switch specifies whether to show or hide the confirmation prompt. How this switch affects the cmdlet depends on if the cmdlet requires confirmation before proceeding.