Replace ClassDB calls with available macros in GDExtension docs

tutorials/scripting/gdextension/gdextension_cpp_example.rst

@@ -268,7 +268,7 @@ GDExtension plugin.
             return;
         }
 
-        ClassDB::register_class<GDExample>();
+        GDREGISTER_CLASS(GDExample);
     }
 
     void uninitialize_example_module(ModuleInitializationLevel p_level) {
@@ -487,7 +487,7 @@ show the methods we end up changing, don't remove the lines we're omitting:
     void GDExample::_bind_methods() {
         ClassDB::bind_method(D_METHOD("get_amplitude"), &GDExample::get_amplitude);
         ClassDB::bind_method(D_METHOD("set_amplitude", "p_amplitude"), &GDExample::set_amplitude);
-        ClassDB::add_property("GDExample", PropertyInfo(Variant::FLOAT, "amplitude"), "set_amplitude", "get_amplitude");
+        ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "amplitude"), "set_amplitude", "get_amplitude");
     }
 
     GDExample::GDExample() {
@@ -544,7 +544,7 @@ showing the methods that have changed so don't remove anything we're omitting:
         ...
         ClassDB::bind_method(D_METHOD("get_speed"), &GDExample::get_speed);
         ClassDB::bind_method(D_METHOD("set_speed", "p_speed"), &GDExample::set_speed);
-        ClassDB::add_property("GDExample", PropertyInfo(Variant::FLOAT, "speed", PROPERTY_HINT_RANGE, "0,20,0.01"), "set_speed", "get_speed");
+        ADD_PROPERTY("GDExample", PropertyInfo(Variant::FLOAT, "speed", PROPERTY_HINT_RANGE, "0,20,0.01"), "set_speed", "get_speed");
     }
 
     GDExample::GDExample() {
@@ -638,7 +638,7 @@ as follows:
 
     void GDExample::_bind_methods() {
         ...
-        ClassDB::add_property("GDExample", PropertyInfo(Variant::FLOAT, "speed", PROPERTY_HINT_RANGE, "0,20,0.01"), "set_speed", "get_speed");
+        ADD_PROPERTY("GDExample", PropertyInfo(Variant::FLOAT, "speed", PROPERTY_HINT_RANGE, "0,20,0.01"), "set_speed", "get_speed");
 
         ADD_SIGNAL(MethodInfo("position_changed", PropertyInfo(Variant::OBJECT, "node"), PropertyInfo(Variant::VECTOR2, "new_pos")));
     }