Add TabGroupsUiImprovementsAndroid to fieldtrial_testing_config

Bug: 956205
Change-Id: I0960ddb12101f35c60c26a70c5592230964ac5ff
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1725521
Auto-Submit: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Commit-Queue: Robert Kaplow <rkaplow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#682290}

testing/variations/fieldtrial_testing_config.json

@@ -5273,6 +5273,21 @@
             ]
         }
     ],
+    "TabGroupsUiImprovementsAndroid": [
+        {
+            "platforms": [
+                "android"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "TabGroupsUiImprovementsAndroid"
+                    ]
+                }
+            ]
+        }
+    ],
     "TabGroupsYourTabsTogether": [
         {
             "platforms": [