Terraform: An argument named "docker_image_name" is not expected here.

Hey there,

I'm attempting to use the Terraform code. With or without modification to dev.tfvars I run the following:

terraform init
terraform plan -var-file='dev.tfvars'

And I get the following errors:
╷
│ Error: Unsupported argument
│
│ on main.tf line 116, in resource "azurerm_linux_web_app" "wordpress_web_app":
│ 116: docker_image_name = "${var.wordpress_container_linux_fx_version}:8.2"
│
│ An argument named "docker_image_name" is not expected here.
╵
╷
│ Error: Unsupported argument
│
│ on main.tf line 117, in resource "azurerm_linux_web_app" "wordpress_web_app":
│ 117: docker_registry_url = var.app_service_docker_registry_url
│
│ An argument named "docker_registry_url" is not expected here.

I am running Terraform 1.6.0 on Windows 11. Same occurs with Terraform 1.5.7. Same happens in Ubuntu 22.04.3 under WSL2 with:

Terraform v1.6.1
on linux_amd64
+ provider registry.terraform.io/azure/azapi v1.9.0
+ provider registry.terraform.io/hashicorp/azurerm v3.30.0
+ provider registry.terraform.io/hashicorp/random v3.5.1