sandbox: add logging-write scope to service account

This should remove another speedbump in viewing logs from sandbox
containers.

Updates golang/go#25224

Change-Id: I24be482ce90b189b0b74dab00a26c6b816592b9f
Reviewed-on: https://go-review.googlesource.com/c/playground/+/214797
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/sandbox/sandbox.tf b/sandbox/sandbox.tf
index e9554dd..e6c84b3 100644
--- a/sandbox/sandbox.tf
+++ b/sandbox/sandbox.tf
@@ -51,7 +51,7 @@
   # See https://cloud.google.com/load-balancing/docs/health-checks
   tags = ["allow-health-checks", "allow-network-lb-health-checks"]
   service_account {
-    scopes = ["storage-ro"]
+    scopes = ["logging-write", "storage-ro"]
   }
   disk {
     source_image = data.google_compute_image.cos.self_link