Adjust the test config for HaTS experiment change

Change-Id: I06f1eff192d85a69365069e4e337d45a4e638b1b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2001084Reviewed-by: Steven Holte <holte@chromium.org>
Commit-Queue: Wei Li <weili@chromium.org>
Cr-Commit-Position: refs/heads/master@{#731830}

testing/variations/fieldtrial_testing_config.json

@@ -2112,7 +2112,7 @@
                     "name": "EnabledNTP79",
                     "params": {
                         "en_site_id": "ty52vxwjrabfvhusawtrmkmx6m",
-                        "probability": "0.2",
+                        "probability": "0.4",
                         "survey": "satisfaction"
                     },
                     "enable_features": [