[terraform] increase ECS task count for Tunnelbroker

Summary: [ENG-9380](https://linear.app/comm/issue/ENG-9380/increase-ecs-task-count-for-tunnelbroker)

Test Plan: terraform plan

Reviewers: bartek

Reviewed By: bartek

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D13491

services/terraform/remote/service_tunnelbroker.tf

@@ -163,12 +163,7 @@ resource "aws_ecs_service" "tunnelbroker" {
   task_definition      = aws_ecs_task_definition.tunnelbroker.arn
   force_new_deployment = true
 
-  desired_count = 1
-  # Allow external changes without Terraform plan difference
-  # We can freely specify replica count in AWS Console
-  lifecycle {
-    ignore_changes = [desired_count]
-  }
+  desired_count = 2
 
   service_connect_configuration {
     enabled = true