{ApplicationGateway} Include the possible value for Operator and Vari…

…able parameter (Azure#18197)

On this page:
https://docs.microsoft.com/en-us/powershell/module/az.network/new-azapplicationgatewayfirewallexclusionconfig?view=azps-7.5.0

It seems it would be useful to document the valid values for the -Variable and -Operator parameters

Fixes Azure#18106

src/Network/Network/help/New-AzApplicationGatewayFirewallExclusionConfig.md

@@ -47,7 +47,7 @@ Accept wildcard characters: False
 ```
 
 ### -Operator
-When variable is a collection, operate on the selector to specify which elements in the collection this exclusion applies to.
+When variable is a collection, operate on the selector to specify which elements in the collection this exclusion applies to. Possible values are Any, IPMatch, GeoMatch, Equal, Contains, LessThan, GreaterThan, LessThanOrEqual, GreaterThanOrEqual, BeginsWith, EndsWith.
 
 ```yaml
 Type: System.String
@@ -77,7 +77,7 @@ Accept wildcard characters: False
 ```
 
 ### -Variable
-The variable to be excluded.
+The variable to be excluded. Match variable. Possible values are RequestHeaderNames, RequestCookieNames, QueryStringArgNames, RequestBodyPostArgNames.
 
 ```yaml
 Type: System.String