[Az.Resources] Adding examples of how to use ServicePrincipalName parameter (#26891)

* Update Get-AzRoleAssignment.md

Adding examples of how to use the 'ServicePrincipalName' parameter.

* Removing example 6

Removed example 6 as it was very similiar to example 5.

Author: SebastianClaesson

src/Resources/Resources/help/Get-AzRoleAssignment.md

@@ -203,6 +203,14 @@ Get-AzRoleAssignment -Scope "/subscriptions/96231a05-34ce-4eb4-aa6a-70759cbb5e83
 
 Gets role assignments at the 'site1' website scope.
 
+### Example 5
+```powershell
+$ApplicationObject = Get-AzADServicePrincipal -DisplayName 'ApplicationDisplayName'
+Get-AzRoleAssignment -ServicePrincipalName $ApplicationObject.AppId
+```
+
+Gets role assignments for the specified Service Principal using Get-AzAdServicePrincipal.
+
 ## PARAMETERS
 
 ### -DefaultProfile