Update for -HostNames parameter values (#13349)

Values provided for -Hostnames should be in separate quotation marks

Author: mahortas

src/Network/Network/help/Add-AzApplicationGatewayHttpListener.md

@@ -60,7 +60,7 @@ The second command adds the listener, which uses the HTTPS protocol, to the appl
 ### Example 3: Add a HTTPS listener with SSL and HostNames
 ```
 PS C:\>$AppGw = Get-AzApplicationGateway -Name "ApplicationGateway01" -ResourceGroupName "ResourceGroup01"
-PS C:\> $AppGw = Add-AzApplicationGatewayHttpListener -ApplicationGateway $AppGw -Name "Listener01" -Protocol "Https" -FrontendIpConfiguration $FIP01 -FrontendPort $FP01 -SslCertificate $SSLCert01 -HostNames "*.contoso.com,www.microsoft.com"
+PS C:\> $AppGw = Add-AzApplicationGatewayHttpListener -ApplicationGateway $AppGw -Name "Listener01" -Protocol "Https" -FrontendIpConfiguration $FIP01 -FrontendPort $FP01 -SslCertificate $SSLCert01 -HostNames "*.contoso.com","www.microsoft.com"
 ```
 
 The first command gets the application gateway and stores it in the $AppGw variable.