Add SecurityWarningIconUpdate field trial to the test bot config files

testing/variations/fieldtrial_testing_config_linux.json

 {
     "AsyncDNS": [
         {
             "group_name": "AsyncDNSA"
         }
     ],
     "AutofillClassifier": [
         {
             "group_name": "Enabled"
         }
@@ skipping 315 matching lines @@
     "SchedulerExpensiveTaskBlocking": [
         {
             "group_name": "Enabled"
         }
     ],
     "SdchPersistence": [
         {
             "group_name": "Enabled"
         }
     ],
+    "SecurityWarningIconUpdate": [
+        {
+            "enable_features": [
+                "SecurityWarningIconUpdate"
+            ],
+            "group_name": "Enabled"
+        },
+        {
+            "disable_features": [
+                "SecurityWarningIconUpdate"
+            ],
+            "group_name": "Control"
+        },
+        {
+            "group_name": "Default"
+        }
+    ],
     "SignInPasswordPromo": [
         {
             "group_name": "Enable",
             "params": {
                 "dismissal_threshold": "1"
             }
         }
     ],
     "SimpleCacheTrial": [
         {
@@ skipping 84 matching lines @@
     ],
     "use-new-media-cache": [
         {
             "enable_features": [
                 "use-new-media-cache"
             ],
             "group_name": "Enabled"
         }
     ]
 }