"az network firewall policy rule-collection-group collection rule add" command does not properly set translatedFqdn

> ### `az feedback` auto-generates most of the information requested below, as of CLI version 2.0.62

**Describe the bug**

When you use the following Azure CLI command and you don't explicitly specify a value for the translatedFqdn property using the --translated-fqdn optional parameter, a NAT rule gets successfully created, but the Azure Firewall and Azure Firewall Policy do not properly route the traffic to the translated address:

az network firewall policy rule-collection-group collection rule add \
--policy-name $firewallPolicyName \
--resource-group $resourceGroupName \
--rule-collection-group-name $ruleCollectionGroupName \
--collection-name $dnatRuleCollectionName \
--name $dnatRuleName \
--rule-type NatRule \
--destination-addresses $firewallPublicIpAddress \
--destination-ports $destinationPort \
--ip-protocols TCP \
--source-addresses '*' \
--translated-port $translatedPort \
--translated-address $serviceExternalIpAddress 1>/dev/null

**To Reproduce**

Try to use the above command to create a NAT rule in a NAT rule collection: the rule will be created, but it won't work properly. If you instead create the same rule using the Azure portal, with the same data, it works as expected.

I used the following command to compare and contrast the rule created by the above Azure CLI command and the rule created by the Azure Portal:

az network firewall policy rule-collection-group collection list \
--policy-name BabosbirdFirewallPolicy \
--rule-collection-group-name DefaultDnatRuleCollectionGroup \
--resource-group BabosbirdRG

The two rules are almost identical, apart from the value of the translatedFqdn property:

- the Azure CLI command sets its value to ""
- the Azure Portal sets its value to null

```json
[
{
"action": {
"type": "Dnat"
},
"name": "DnatRules",
"priority": 100,
"ruleCollectionType": "FirewallPolicyNatRuleCollection",
"rules": [
{
"description": null,
"destinationAddresses": [
"51.124.64.22"
],
"destinationPorts": [
"80"
],
"ipProtocols": [
"TCP"
],
"name": "CreatedViaAzureCLI",
"ruleType": "NatRule",
"sourceAddresses": [
"*"
],
"sourceIpGroups": [],
"translatedAddress": "51.137.8.127",
"translatedFqdn": null,
"translatedPort": "80"
},
{
"description": null,
"destinationAddresses": [
"51.124.64.22"
],
"destinationPorts": [
"80"
],
"ipProtocols": [
"TCP"
],
"name": "CreatedViaThePortal",
"ruleType": "NatRule",
"sourceAddresses": [
"*"
],
"sourceIpGroups": [],
"translatedAddress": "51.137.8.127",
"translatedFqdn": "",
"translatedPort": "80"
}
]
}
]
```

**Expected behavior**

Please fix the Azure CLI so that the NAT rule properly routes the incoming traffic on the destination address to the translated address.

**Environment summary**

Tested using bash scripts in Azure DevOps and locally on WSL.

**Additional context**