Add the experiment to fieldtrial_testing_config

Added experiment: InvalidateBookmarkSyncMetadataIfClientTagMissing.

Bug: None
Change-Id: Ib72d022f5292ec8fc9a10cdb73d92ff37391f74f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2494880Reviewed-by: Jesse Doherty <jwd@chromium.org>
Commit-Queue: Rushan Suleymanov <rushans@google.com>
Cr-Commit-Position: refs/heads/master@{#821184}

testing/variations/fieldtrial_testing_config.json

@@ -3769,6 +3769,27 @@
             ]
         }
     ],
+    "InvalidateBookmarkSyncMetadataIfClientTagMissing": [
+        {
+            "platforms": [
+                "android",
+                "android_webview",
+                "chromeos",
+                "ios",
+                "linux",
+                "mac",
+                "windows"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "InvalidateBookmarkSyncMetadataIfClientTagMissing"
+                    ]
+                }
+            ]
+        }
+    ],
     "IsolatePasswordSites": [
         {
             "platforms": [