ci: update Terraform to 0.4.11

Changelogs:
- https://github.com/hashicorp/terraform/blob/v0.14/CHANGELOG.md
- https://www.terraform.io/language/upgrade-guides/0-14
- https://www.hashicorp.com/blog/announcing-hashicorp-terraform-0-14-general-availability
- https://www.hashicorp.com/blog/terraform-0-14-adds-a-new-concise-diff-format-to-terraform-plans
- https://www.hashicorp.com/blog/terraform-0-14-adds-the-ability-to-redact-sensitive-values-in-console-output
- https://www.hashicorp.com/blog/terraform-0-14-introduces-a-dependency-lock-file-for-providers

Part of #1613

[skip ci]

Author: php-coder

infra/terraform/.terraform-version

@@ -1 +1 @@
-0.13.7
+0.14.11

infra/terraform/.terraform.lock.hcl

@@ -5,6 +5,7 @@ variable "do_token" {
   # How to obtain a token: https://docs.digitalocean.com/reference/api/create-personal-access-token/
   description = "Digital Ocean Personal Access Token"
   type        = string
+  sensitive   = true
 }
 
 variable "uptimerobot_token" {
@@ -14,6 +15,7 @@ variable "uptimerobot_token" {
   # - scroll down to API Settings and select "Main API Key"
   description = "UptimeRobot API key"
   type        = string
+  sensitive   = true
 }
 
 # Digital Ocean provider docs: https://registry.terraform.io/providers/digitalocean/digitalocean/2.28.1/docs

infra/terraform/my-stamps.tf

@@ -1,6 +1,6 @@
 terraform {
   # @todo #1268 Update Terraform to 0.15.x
-  required_version = ">= 0.13"
+  required_version = ">= 0.14"
 
   required_providers {
     digitalocean = {