enable retina by default because retina disabling was broken in catalina

samples/sources/sample_00/sample_00.cpp

@@ -186,7 +186,7 @@ namespace
 
             the<render>().execute(render::command_block<64>()
                 .add_command(render::viewport_command(
-                    the<window>().real_size()))
+                    the<window>().framebuffer_size()))
                 .add_command(render::clear_command()
                     .color_value({1.f, 0.4f, 0.f, 1.f}))
                 .add_command(render::draw_command(material_, geometry_)));