Remove "delay_tcp_race": "true" from QUIC testing variations since it is now on by default and not …

testing/variations/fieldtrial_testing_config_ios.json

 {
     "AutofillFieldMetadata": [
         {
             "group_name": "Enabled"
         }
     ],
     "AutofillProfileCleanup": [
         {
             "enable_features": [
                 "AutofillProfileCleanup"
@@ skipping 71 matching lines @@
                 "PersistentHistograms"
             ],
             "group_name": "EnabledOnDisk",
             "params": {
                 "storage": "MappedFile"
             }
         }
     ],
     "QUIC": [
         {
-            "group_name": "Enabled",
-            "params": {
-                "delay_tcp_race": "true"
-            }
+            "group_name": "Enabled"
         }
     ],
     "SdchPersistence": [
         {
             "group_name": "Enabled"
         }
     ],
     "SecurityWarningIconUpdate": [
         {
             "enable_features": [
@@ skipping 18 matching lines @@
         {
             "group_name": "Disabled"
         }
     ],
     "TabSyncByRecency": [
         {
             "group_name": "Enabled"
         }
     ]
 }