fix: 💥 standard_gravity removed from si2019 namespace as it is not an SI defining constant

example/aliases/box_example.cpp

@@ -40,7 +40,7 @@ namespace {
 
 using namespace units::aliases::isq::si;
 
-inline constexpr auto g = units::isq::si::si2019::standard_gravity<>;  // NOLINT(readability-identifier-length)
+inline constexpr auto g = units::isq::si::standard_gravity<>;  // NOLINT(readability-identifier-length)
 inline constexpr auto air_density = kg_per_m3<>(1.225);
 
 class Box {

example/literals/box_example.cpp

@@ -47,7 +47,7 @@ using kg = si::kilogram;
 using N = si::newton;
 using kgpm3 = si::kilogram_per_metre_cub;
 
-inline constexpr auto g = si::si2019::standard_gravity<>;
+inline constexpr auto g = si::standard_gravity<>;
 inline constexpr si::density<kgpm3> air_density(1.225);
 
 

example/references/box_example.cpp

@@ -42,7 +42,7 @@ using namespace units::isq;
 using namespace si::mass_references;
 using namespace si::volume_references;
 
-inline constexpr Acceleration auto g = si::si2019::standard_gravity<>;
+inline constexpr Acceleration auto g = si::standard_gravity<>;
 inline constexpr Density auto air_density = 1.225 * (kg / m3);
 
 class Box {