chore: remove redundant type conversions

It's redundant code because custom data comparison logics(`CustomEqualityEquivalencyStep`) are added at recent commit

src/Docfx.DataContracts.Common/JTokenConverter.cs

@@ -21,23 +21,6 @@ public static T Convert<T>(object obj)
             return jToken.ToObject<T>();
         }
 
-        // Custom code path for `System.Text.Json` deserialization.
-        // `ObjectToInferredTypesConverter` deserialize items as `List<object>`.
-        // So it need to convert `List<object>` to `List<TItem>`.
-        if (obj is List<object> list && IsListType<T>())
-        {
-            var json = JsonUtility.Serialize(list);
-            var result = JsonUtility.Deserialize<T>(new StringReader(json));
-            return result;
-        }
-
         throw new InvalidCastException();
     }
-
-    private static bool IsListType<T>()
-    {
-        var type = typeof(T);
-        return type.GetTypeInfo().IsGenericType
-            && type.GetGenericTypeDefinition() == typeof(List<>);
-    }
 }