Fix another CodeQL issue (#5570)

Author: HongGit

.CodeQL.yml

@@ -4,6 +4,6 @@
 
 path_classifiers:
   refs:
-    # The test/ directories don't contain shipping implementations of code, so they should
+    # The tests/ directories don't contain shipping implementations of code, so they should
     # be excluded from analysis. 
     - src/**/tests/*

src/dotnet-svcutil/lib/src/Shared/Options/OptionsSerializer.cs

@@ -131,7 +131,7 @@ public override void WriteJson(JsonWriter writer, object value, JsonSerializer s
 
         public static void WriteJson(JsonWriter writer, TAppOptions options, JsonSerializer serializer)
         {
-            serializer.TypeNameHandling = TypeNameHandling.Auto;
+            serializer.TypeNameHandling = TypeNameHandling.None;
 
             ((IOptionsSerializationHandler)options).RaiseBeforeSerializeEvent();