Add fieldtrial_testing entry for OmniboxOnFocusSuggestions on iOS

Bug: 1048193
Change-Id: I111ceead01455b046f98c6da557aa1430679d0a5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2124651Reviewed-by: Brian White <bcwhite@chromium.org>
Commit-Queue: Robbie Gibson <rkgibson@google.com>
Cr-Commit-Position: refs/heads/master@{#754893}

testing/variations/fieldtrial_testing_config.json

@@ -3690,7 +3690,14 @@
             "experiments": [
                 {
                     "name": "iOSExperiments",
-                    "enable_features": []
+                    "params": {
+                        "ZeroSuggestVariant:1:*": "RemoteNoUrl",
+                        "ZeroSuggestVariant:7:*": "RemoteNoUrl",
+                        "ZeroSuggestVariant:8:*": "RemoteNoUrl"
+                    },
+                    "enable_features": [
+                        "OmniboxOnFocusSuggestions"
+                    ]
                 }
             ]
         }