[test_problems] Remove checks for legacy VS versions

_MSC_VER < 1900 corresponds to 1800 and earlier, which is
VC++ version 12.0 (Visual Studio 2013). Cantera now uses the C++17
standard, with the current minimum requirement VC++ version 14.1
(Visual Studio 2017).

test_problems/multiGasTransport/multiGasTransport.cpp

@@ -39,9 +39,6 @@ static double cutoff(double val, double atol=1.0E-15)
 
 int main(int argc, char** argv)
 {
-#if defined(_MSC_VER) && _MSC_VER < 1900
-    _set_output_format(_TWO_DIGIT_EXPONENT);
-#endif
     try {
         auto sol = newSolution("gri30.yaml", "gri30", "Multi");
         auto gas = sol->thermo();