[cobalt] - Replace "system-temp" with "isolated-temp".

This change replaces global temp in test with system temps.
Bug: 25092

Change-Id: I17bf15887fa42145d0fbe72630a3b7b68f938c2b
diff --git a/meta/cobalt_core_tests.cmx b/meta/cobalt_core_tests.cmx
index 1e930e8..261b7be 100644
--- a/meta/cobalt_core_tests.cmx
+++ b/meta/cobalt_core_tests.cmx
@@ -4,7 +4,7 @@
   },
   "sandbox": {
     "features": [
-      "system-temp",
+      "isolated-temp",
       "deprecated-ambient-replace-as-executable"
     ]
   }