[TTS] Default-enable the Definitions experiment.

This enables the ContextualSearchDefinitions feature for all builds.

We've pushed this to 1% Stable on M77 and the metrics look good, so
default-enabling for M82 (will revert if the experiment has snags).

BUG=943885

Change-Id: Id35ce0f8ff4bca54163efb0f1231e1b2e61f7c07
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2070962Reviewed-by: Ilya Sherman <isherman@chromium.org>
Commit-Queue: Donn Denman <donnd@chromium.org>
Cr-Commit-Position: refs/heads/master@{#744186}

chrome/browser/flags/android/chrome_feature_list.cc

@@ -409,7 +409,7 @@ const base::Feature kContextMenuSearchWithGoogleLens{
     "ContextMenuSearchWithGoogleLens", base::FEATURE_DISABLED_BY_DEFAULT};
 
 const base::Feature kContextualSearchDefinitions{
-    "ContextualSearchDefinitions", base::FEATURE_DISABLED_BY_DEFAULT};
+    "ContextualSearchDefinitions", base::FEATURE_ENABLED_BY_DEFAULT};
 
 const base::Feature kContextualSearchLongpressResolve{
     "ContextualSearchLongpressResolve", base::FEATURE_DISABLED_BY_DEFAULT};

testing/variations/fieldtrial_testing_config.json

@@ -1548,21 +1548,6 @@
             ]
         }
     ],
-    "ContextualSearchDefinitions": [
-        {
-            "platforms": [
-                "android"
-            ],
-            "experiments": [
-                {
-                    "name": "ContextualSearchDefinitions",
-                    "enable_features": [
-                        "ContextualSearchDefinitions"
-                    ]
-                }
-            ]
-        }
-    ],
     "CopylessPaste": [
         {
             "platforms": [