Fix vkcube-on-scenic

I accidentally removed fuchsia.ui.scenic.Scenic from the list of
services in commit 203572ccdb2bd105b5627de6b877a437cb599a4c.

Change-Id: Ib1d5461487beb0200ed15da380bf4101af6260b0
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/Vulkan-Tools/+/459954
Reviewed-by: Craig Stout <cstout@google.com>
diff --git a/cube/fuchsia/meta/vkcube-on-scenic.cmx b/cube/fuchsia/meta/vkcube-on-scenic.cmx
index 7f80377..893a226 100644
--- a/cube/fuchsia/meta/vkcube-on-scenic.cmx
+++ b/cube/fuchsia/meta/vkcube-on-scenic.cmx
@@ -5,5 +5,10 @@
     ],
     "program": {
         "binary": "bin/vkcube-on-scenic"
+    },
+    "sandbox": {
+        "services": [
+            "fuchsia.ui.scenic.Scenic"
+        ]
     }
 }