[DeviceSync v2] Add v2 DeviceSync to field trial testing config file

Ensures test coverage for active CryptAuth v2 DeviceSync field trial.
See
https://chromium.googlesource.com/chromium/src.git/+/master/testing/variations/

The change was made due to a Finch warning in cl/331561231.

Bug: 951969
Change-Id: I62e19971aa831216056e79e1b543022b5148df7c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2410745
Auto-Submit: Josh Nohle <nohle@chromium.org>
Commit-Queue: Steven Holte <holte@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Cr-Commit-Position: refs/heads/master@{#808536}

testing/variations/fieldtrial_testing_config.json

@@ -1899,6 +1899,21 @@
             ]
         }
     ],
+    "CryptAuthV2DeviceSync": [
+        {
+            "platforms": [
+                "chromeos"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled_20200427",
+                    "enable_features": [
+                        "CryptAuthV2DeviceSync"
+                    ]
+                }
+            ]
+        }
+    ],
     "CryptAuthV2Enrollment": [
         {
             "platforms": [