[Remote suggestions] Update the testing config

This CL updates the testing config for the next round of Stable
experiments.

Bug: 738007
Change-Id: Icc30529156bdc9b8149aae1f1cbfbd4527e98c18
Reviewed-on: https://chromium-review.googlesource.com/806534Reviewed-by: Mark Pearson <mpearson@chromium.org>
Commit-Queue: Jan Krcal <jkrcal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521630}

testing/variations/fieldtrial_testing_config.json

@@ -1954,7 +1954,11 @@
             ],
             "experiments": [
                 {
-                    "name": "ReducedPersistent",
+                    "name": "MoreFrequentTierTwo",
+                    "params": {
+                        "soft_fetching_interval_hours-fallback-active_ntp_user": "4",
+                        "soft_fetching_interval_hours-wifi-active_ntp_user": "4"
+                    },
                     "enable_features": [
                         "NTPArticleSuggestions"
                     ]