Typo in variable name in the module `azurerm/Firewall-LB-DNAT-Rule-Collection`

[Dilhasha]

The variable field nat_rule_name_shortned at [1] needs to be corrected asnat_rule_name_shortened.

[1] https://github.com/wso2/azure-terraform-modules/blob/main/modules/azurerm/Firewall-LB-DNAT-Rule-Collection/variables.tf#L36