Do not use WeaklyRegular with Xcode 15 for type detection

Removing the `WeaklyRegular` requirement from the `Scalar`, `Complex`,
and `Vector` concepts seems to address compiler crashes or long
compilation times with apple-clang included in Xcode 15.

I thought I had previously tried removing the `WeaklyRegular`
requirement and it had not solved the problem but either I made a
mistake with this test or some other changes after rebasing this work
changed the situation.

test/static/concepts_test.cpp

@@ -20,7 +20,6 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#include <mp-units/bits/hacks.h>
 #include <mp-units/systems/isq/space_and_time.h>
 #include <mp-units/systems/natural.h>
 #include <mp-units/systems/si.h>
@@ -309,9 +308,7 @@ static_assert(!RepresentationOf<std::complex<double>, quantity_character::scalar
 static_assert(!RepresentationOf<std::complex<double>, quantity_character::vector>);
 static_assert(!RepresentationOf<std::complex<double>, quantity_character::tensor>);
 static_assert(RepresentationOf<cartesian_vector<double>, quantity_character::vector>);
-#ifndef MP_UNITS_APPLE_CLANG_HACKS
 static_assert(!RepresentationOf<cartesian_vector<double>, quantity_character::scalar>);
-#endif
 static_assert(!RepresentationOf<cartesian_vector<double>, quantity_character::complex>);
 static_assert(!RepresentationOf<cartesian_vector<double>, quantity_character::tensor>);
 static_assert(!RepresentationOf<std::chrono::seconds, quantity_character::scalar>);

test/static/quantity_test.cpp

@@ -65,8 +65,6 @@ static_assert(sizeof(quantity<isq::length[m]>) == sizeof(double));
 static_assert(sizeof(quantity<si::metre, short>) == sizeof(short));
 static_assert(sizeof(quantity<isq::length[m], short>) == sizeof(short));
 
-#ifndef MP_UNITS_APPLE_CLANG_HACKS
-
 template<template<auto, typename> typename Q>
 concept invalid_types = requires {
   requires !requires { typename Q<isq::dim_length, double>; };  // dimension instead of reference
@@ -86,8 +84,6 @@ concept invalid_types = requires {
 };
 static_assert(invalid_types<quantity>);
 
-#endif
-
 static_assert(std::is_trivially_default_constructible_v<quantity<isq::length[m]>>);
 static_assert(std::is_trivially_copy_constructible_v<quantity<isq::length[m]>>);
 static_assert(std::is_trivially_move_constructible_v<quantity<isq::length[m]>>);