Updated the Sku parameter's description

Fixed misspelled word ("Fre" to "Free").  Changed example values to use the PowerShell hashtable syntax.  Added example values for using the Standard tier.

Author: rcabr

src/ResourceManager/Resources/Commands.Resources/help/New-AzureRmPolicyAssignment.md

@@ -445,7 +445,7 @@ Accept wildcard characters: False
 ```
 
 ### -Sku
-A hash table which represents sku properties. Defaults to Free Sku: Name = A0, Tier = Fre
+A hash table which represents SKU properties. Defaults to the Free SKU with the values: `@{Name = 'A0'; Tier = 'Free'}`. To use the Standard SKU, use the values: `@{Name = 'A1'; Tier = 'Standard'}`.
 
 ```yaml
 Type: System.Collections.Hashtable