Enable SmartDimModelV3 by default

This feature has happy results at 1% stable. See crbug.com/937063#c37
for details & discussion.

Also remove fieldtrial testing config.

Bug: 937063
Change-Id: Id61da3286a9ce5239d1ad9715eeac5b2d7056bbe
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2563194
Commit-Queue: Andrew Moylan <amoylan@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#832674}

chromeos/constants/chromeos_features.cc

@@ -608,7 +608,7 @@ const base::Feature kSmartDimNewMlAgent{"SmartDimNewMlAgent",
 // Uses the V3 (~2019-05 era) Smart Dim model instead of the default V2
 // (~2018-11) model.
 const base::Feature kSmartDimModelV3{"SmartDimModelV3",
-                                     base::FEATURE_DISABLED_BY_DEFAULT};
+                                     base::FEATURE_ENABLED_BY_DEFAULT};
 
 // This feature:
 // - Creates a new "Sync your settings" section in Chrome OS settings

testing/variations/fieldtrial_testing_config.json

@@ -6492,25 +6492,6 @@
             ]
         }
     ],
-    "SmartDimModelV3": [
-        {
-            "platforms": [
-                "chromeos"
-            ],
-            "experiments": [
-                {
-                    "name": "Enabled_20200207",
-                    "params": {
-                        "dim_threshold": "-0.5"
-                    },
-                    "enable_features": [
-                        "SmartDimModelV3",
-                        "UserActivityPrediction"
-                    ]
-                }
-            ]
-        }
-    ],
     "SplitCacheByNetworkIsolationKey": [
         {
             "platforms": [