Update hashicorp/azurerm requirement in /08_aks_app_gateway

Updates the requirements on [hashicorp/azurerm](https://github.com/hashicorp/terraform-provider-azurerm) to permit the latest version.
- [Release notes](https://github.com/hashicorp/terraform-provider-azurerm/releases)
- [Changelog](https://github.com/hashicorp/terraform-provider-azurerm/blob/main/CHANGELOG.md)
- [Commits](hashicorp/terraform-provider-azurerm@v2.0.0...v3.111.0)

---
updated-dependencies:
- dependency-name: hashicorp/azurerm
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

08_aks_app_gateway/providers.tf

@@ -5,7 +5,7 @@ terraform {
   required_providers {
     azurerm = {
       source  = "hashicorp/azurerm"
-      version = "~>2.0"
+      version = "~>3.111"
     }
   }
 }