terraform: increase workers to 5 for dev and prod

- Match the max constainer instances for the Cloud Run configuration.

Change-Id: I76c9dd3bce72363131ca0bbedb1bac7323985548
Reviewed-on: https://go-review.googlesource.com/c/pkgsite-metrics/+/702078
Reviewed-by: Markus Kusano <kusano@google.com>
Auto-Submit: Ethan Lee <ethanalee@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

terraform/environment/worker.tf

diff --git a/terraform/environment/worker.tf b/terraform/environment/worker.tf
index 0356d63..282179d 100644
--- a/terraform/environment/worker.tf
+++ b/terraform/environment/worker.tf
@@ -208,7 +208,7 @@
 # Other components.
 
 resource "google_cloud_tasks_queue" "worker_queues" {
-  count = 4
+  count = 5
   project  = var.project
   name     = "${var.env}-worker-queue-${count.index}"
   location = var.region