Replace std::result_of with std::invoke_result.
Fixing an error C2039 'result_of': is not a member of 'std' HydroMechanics C:\Users...\ogs\ProcessLib\Output\SecondaryVariable.h 55
The std::result_of is deprecated since c++17.
Fixing an error C2039 'result_of': is not a member of 'std' HydroMechanics C:\Users...\ogs\ProcessLib\Output\SecondaryVariable.h 55
The std::result_of is deprecated since c++17.