chore(e2e): Modify gcp label to meet format constraints (#5400)

GCP label constraints include the following:

The value can only contain lowercase letters, numeric characters, underscores and dashes. The value can be at most 63 characters long. International characters are allowed.

enos/modules/gcp_target/main.tf

@@ -125,7 +125,7 @@ resource "google_compute_instance" "boundary_target" {
     "project" : "enos",
     "project_name" : "qti-enos-boundary",
     "environment" : var.environment,
-    "enos_user" : var.enos_user,
+    "enos_user" : replace(var.enos_user, "/[\\W]+/", ""),
     "filter_label_1" : random_id.filter_label1.hex
     "filter_label_2" : random_id.filter_label2.hex
   })