Update field trial config for no persistent store

Bug: 1112500
Change-Id: I86909b9361fa2d438a258a1fb03b65d40f277cc9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2427206Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Commit-Queue: Sophie Chang <sophiechang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#814099}

testing/variations/fieldtrial_testing_config.json

@@ -4908,12 +4908,14 @@
             ],
             "experiments": [
                 {
-                    "name": "Enabled_20200814",
+                    "name": "Enabled",
                     "params": {
+                        "batch_update_hints_for_top_hosts": "false",
                         "persist_hints_to_disk": "false"
                     },
                     "enable_features": [
-                        "OptimizationHints"
+                        "OptimizationHints",
+                        "OptimizationHintsFetching"
                     ]
                 }
             ]