Add fieltrial group for password search feature

In order to proceed the rollout for the password search feature in
http://cl/189730122, add the test group to the field trial config.

Change-Id: I281c4908826fee3247a66a29f94699044c9ec03e
Reviewed-on: https://chromium-review.googlesource.com/970344Reviewed-by: Gayane Petrosyan <gayane@chromium.org>
Commit-Queue: Friedrich Horschig <fhorschig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#544368}

testing/variations/fieldtrial_testing_config.json

@@ -2500,6 +2500,21 @@
             ]
         }
     ],
+    "PasswordManagerSearchSettings": [
+        {
+            "platforms": [
+                "android"
+            ],
+            "experiments": [
+                {
+                    "name": "PasswordSearchEnabled",
+                    "enable_features": [
+                        "PasswordSearchMobile"
+                    ]
+                }
+            ]
+        }
+    ],
     "PasswordProtectionForEnterprise": [
         {
             "platforms": [