[Smart Selection] Update fieldtrial_testing_config

Updates the config to match our full launch group for
Smart Selection on Chrome for Android.

BUG=770767

Change-Id: I80a04f3b66342eba17c17c8b66cda9b25d7b278b
Reviewed-on: https://chromium-review.googlesource.com/809850
Commit-Queue: Alexei Svitkine <asvitkine@chromium.org>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521915}

testing/variations/fieldtrial_testing_config.json

@@ -852,7 +852,7 @@
             ],
             "experiments": [
                 {
-                    "name": "Enabled",
+                    "name": "Enabled_Launch",
                     "enable_features": [
                         "ChromeSmartSelection"
                     ]