message: Remove c++17 support flag in cmake
  Already covered by AppVeyor
diff: @@ -80,11 +80,6 @@ if(MSVC)
  # Disable warning C4566: character represented by universal-character-name '\uFF01' cannot be represented in the current code page (1252)
  # Disable warning C4996: 'nlohmann::basic_json<std::map,std::vector,std::string,bool,int64_t,uint64_t,double,std::allocator,nlohmann::adl_serializer>::operator <<': was declared deprecated
  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /wd4389 /wd4309 /wd4566 /wd4996")
  -
  - if(MSVC_VERSION GREATER_EQUAL 1910)
  - # Enable c++17 support in Visual Studio 2017 (for testing perfect forwarding and transparent comparator in find() / count())
  - set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /std:c++17")
  - endif()
  endif()
  #############################################################################
  