Set C++ standard back to C++17 to match develop branch

Author: divyaprakash-iitd

meson.build

@@ -6,7 +6,7 @@ project('SU2', 'c', 'cpp',
         default_options: ['buildtype=release',
                           'warning_level=0',
                           'c_std=c99',
-                          'cpp_std=c++11',
+                          'cpp_std=c++17',
                           'tracy_enable=false'])
 
 fsmod = import('fs')