LibWeb: Convert Layout::Node to new pixel units

Author: https://github.com/AtkinsSJ
Commit: 5d8e3f5122
Pull-request: https://github.com/SerenityOS/serenity/pull/16514
Reviewed-by: https://github.com/MacDue
Reviewed-by: https://github.com/linusg ✅

Userland/Libraries/LibWeb/CSS/StyleProperties.cpp

@@ -138,7 +138,7 @@ NonnullRefPtr<Gfx::Font> StyleProperties::font_fallback(bool monospace, bool bol
     return Platform::FontPlugin::the().default_font();
 }
 
-float StyleProperties::line_height(Layout::Node const& layout_node) const
+CSSPixels StyleProperties::line_height(Layout::Node const& layout_node) const
 {
     auto line_height = property(CSS::PropertyID::LineHeight);