refactor: 💥 is_XXX customization points for representation types removed

test/static/natural_test.cpp

@@ -22,10 +22,6 @@
 
 #include <mp-units/systems/natural.h>
 
-template<class T>
-  requires mp_units::is_scalar<T>
-constexpr bool mp_units::is_vector<T> = true;
-
 namespace {
 
 using namespace mp_units;