Updates Enable-AzCdnCustomDomainCustomHttps Doc (Azure#20165)

The example for Enable-AzCdnCustomDomainCustomHttps calls New-AzCdnManagedHttpsParameters with TLS12 as the ProtocolType even though that is an invalid value. I'm replacing the ProtocolType value with ServerNameIndication, which is one of the two valid values (ServerNameIndication and IPBased).

Author: patchin404

src/Cdn/help/Enable-AzCdnCustomDomainCustomHttps.md

@@ -33,7 +33,7 @@ Enable https delivery of the custom domain.
 
 ### Example 1: Enable an AzureCDN custom domain under the AzureCDN endpoint
 ```powershell
-$customDomainHttpsParameter = New-AzCdnManagedHttpsParametersObject -CertificateSourceParameterCertificateType Dedicated -CertificateSource Cdn  -ProtocolType TLS12
+$customDomainHttpsParameter = New-AzCdnManagedHttpsParametersObject -CertificateSourceParameterCertificateType Dedicated -CertificateSource Cdn  -ProtocolType ServerNameIndication
 Enable-AzCdnCustomDomainCustomHttps -ResourceGroupName testps-rg-da16jm -ProfileName cdn001 -EndpointName endptest001 -CustomDomainName customdomain001 -CustomDomainHttpsParameter $customDomainHttpsParameter
 ```