Fixed multiple hostnames param for app gateway http listener (Azure#19451)

Author: moo2u2

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

@@ -63,7 +63,7 @@ This command creates an HTTP listener named Listener01, FirewallPolicy as $firew
 
 ### Example 4: Add a HTTPS listener with SSL and HostNames
 ```powershell
-$Listener = New-AzApplicationGatewayHttpListener -Name "Listener01" -Protocol "Https" -FrontendIpConfiguration $FIp01 -FrontendPort $FP01 -SslCertificate $SSLCert01 -HostNames "*.contoso.com,www.microsoft.com"
+$Listener = New-AzApplicationGatewayHttpListener -Name "Listener01" -Protocol "Https" -FrontendIpConfiguration $FIp01 -FrontendPort $FP01 -SslCertificate $SSLCert01 -HostNames "*.contoso.com","www.microsoft.com"
 ```
 
 This command creates an HTTP listener that uses SSL offload and provides the SSL certificate in the $SSLCert01 variable along with two HostNames.