Remove V8 serialize options from fieldtrial config.

testing/variations/fieldtrial_testing_config_mac.json

 {
     "AutofillClassifier": [
         {
             "group_name": "Enabled"
         }
     ],
     "AutofillFieldMetadata": [
         {
             "group_name": "Enabled"
         }
@@ skipping 279 matching lines @@
         }
     ],
     "TranslateUiLangTrial": [
         {
             "group_name": "DefaultTranslateLanguage"
         },
         {
             "group_name": "EnabledTranslateLanguage"
         }
     ],
-    "V8SerializeOptions": [
-        {
-            "enable_features": [
-                "V8_Serialize_Eager",
-                "V8_Serialize_Age_Code"
-            ],
-            "group_name": "SerializeEagerAndAgeCode"
-        }
-    ],
     "VarationsServiceControl": [
         {
             "group_name": "Interval_30min",
             "params": {
                 "fetch_period_min": "30"
             }
         }
     ],
     "ViewsSimplifiedFullscreenUI": [
         {
@@ skipping 28 matching lines @@
     ],
     "use-new-media-cache": [
         {
             "enable_features": [
                 "use-new-media-cache"
             ],
             "group_name": "Enabled"
         }
     ]
 }