Upgrade VMs type and number of nodes for GKE cluster (#4650)

Following the work being done to migrate chrome-tests-syncer to k8s, it
was noticed that the current spec of GKE clusters is not enough for
scheduling the tests-syncer as a k8s cronjob. During the tests done, the
cronjob never gets schedule due to insufficient resources (memory/cpu).
Thus, this PR aims at upgrading the machine types and the number of
nodes available.

Related bug: b/389048599

Co-authored-by: Vitor Guidi <[email protected]>

infra/terraform/variables.tf

@@ -36,12 +36,12 @@ variable "ip_cidr_range" {
 }
 
 variable "gke_num_nodes" {
-  default     = 2
+  default     = 5
   description = "The number of gke nodes"
 }
 
 variable "machine_type" {
-  default     = "e2-standard-2"
+  default     = "e2-standard-4"
   description = "The machine type"
 }