Deploying Azure Linux web app with Terraform results in unsupported block error for app_settings

I am trying to deploy a linux web app using Terraform.

resource "azurerm_linux_web_app" "web_app" {
  name                = "pi"
  resource_group_name = azurerm_resource_group.resource_group.name
  location            = azurerm_service_plan.service_plan.location
  service_plan_id     = azurerm_service_plan.service_plan.id

  site_config {
  }

  app_settings {
    MYSETTING = "some value"
  }
}

I am using provider version 3.89.0 (latest at time of writing)

  required_version = ">=1.6.0"

  required_providers {
    azurerm = {
      source  = "hashicorp/azurerm"
      version = "3.89.0"
    }
  }

I get the following error when I run my terraform script in my Devops piepline;

Error: Unsupported block type on main.tf line 125, in resource
"azurerm_linux_web_app" "web_app":
125: app_settings { Blocks of
type "app_settings" are not expected here.

Did you mean to define
argument "app_settings"? If so, use the equals sign to assign it a
value.

Unless I’m misreading it, the documentation states that there is such a block. The error is pretty clear and I need to pass in some app_settings values. Does anyone know why I might be having these issues and how I might resolve them?

Thanks.