Add a secondary feature name to track for GroupSuggestionsBySearchVsUrl.

Bug: 990865
Change-Id: I2e6535d6f7d33632b660a0f2a72b3c17a423bdf8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1761343Reviewed-by: Mark Pearson <mpearson@chromium.org>
Commit-Queue: Ender <ender@google.com>
Auto-Submit: Ender <ender@google.com>
Cr-Commit-Position: refs/heads/master@{#689007}

testing/variations/fieldtrial_testing_config.json

@@ -3883,7 +3883,8 @@
                 {
                     "name": "Enabled",
                     "enable_features": [
-                        "OmniboxGroupSuggestionsBySearchVsUrl"
+                        "OmniboxGroupSuggestionsBySearchVsUrl",
+                        "OmniboxPreserveDefaultMatchScore"
                     ]
                 }
             ]