ci: update Terraform to 1.1.9

Changelogs:
- https://www.terraform.io/language/upgrade-guides/1-1
- https://github.com/hashicorp/terraform/blob/v1.1/CHANGELOG.md
- https://www.hashicorp.com/blog/terraform-1-1-improves-refactoring-and-the-cloud-cli-experience

Part of #1720

[skip ci]

Author: php-coder

infra/terraform/.terraform-version

@@ -1 +1 @@
-1.0.11
+1.1.9

infra/terraform/versions.tf

@@ -1,5 +1,5 @@
 terraform {
-  required_version = ">= 1.0"
+  required_version = ">= 1.1"
 
   required_providers {
     digitalocean = {