minor build warning fix for C# client

samples/client/petstore/csharp/SwaggerClient/src/IO.Swagger/Client/SwaggerDateConverter.cs

@@ -18,10 +18,13 @@ namespace IO.Swagger.Client
     /// </summary>
     public class SwaggerDateConverter : IsoDateTimeConverter
     {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="SwaggerDateConverter" /> class.
+        /// </summary>
         public SwaggerDateConverter()
         {
             // full-date   = date-fullyear "-" date-month "-" date-mday
             DateTimeFormat = "yyyy-MM-dd";
         }
     }
-}
+}