LibGUI: Remove spacing between day labels in Calendar

Provides better centering over columns.

Libraries/LibGUI/Calendar.cpp

@@ -68,6 +68,7 @@ Calendar::Calendar(Core::DateTime date_time)
     m_day_name_container->set_layout<GUI::HorizontalBoxLayout>();
     m_day_name_container->set_size_policy(GUI::SizePolicy::Fill, GUI::SizePolicy::Fixed);
     m_day_name_container->set_preferred_size(0, 16);
+    m_day_name_container->layout()->set_spacing(0);
     m_day_name_container->set_fill_with_background_color(true);
     m_day_name_container->set_background_role(Gfx::ColorRole::HoverHighlight);
     for (auto& day : m_day_names) {