🐛 Relax operator access syntax for MSVC (#132)

Author: prince-chrismc

include/jwt-cpp/jwt.h

@@ -1800,7 +1800,7 @@ namespace jwt {
 
 		template<typename object_type, typename value_type, typename string_type>
 		using is_subcription_operator_signature =
-			typename std::is_same<decltype(std::declval<object_type>().operator[](std::declval<const string_type>())),
+			typename std::is_same<decltype(std::declval<object_type>()[std::declval<const string_type>()]),
 								  value_type&>;
 
 		template<typename object_type, typename value_type, typename string_type>