LibWeb: Delete unused is_fixed_position from PushStackingContextParams

Author: https://github.com/kalenikaliaksandr
Commit: 8e3a42c54e
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/5609
Reviewed-by: https://github.com/gmta ✅

Libraries/LibWeb/Painting/DisplayListRecorder.h

@@ -123,7 +123,6 @@ public:
         float opacity;
         Gfx::CompositingAndBlendingOperator compositing_and_blending_operator;
         bool isolate;
-        bool is_fixed_position;
         StackingContextTransform transform;
         Optional<Gfx::Path> clip_path = {};
     };

Libraries/LibWeb/Painting/StackingContext.cpp

@@ -323,7 +323,6 @@ void StackingContext::paint(PaintContext& context) const
         .opacity = opacity,
         .compositing_and_blending_operator = compositing_and_blending_operator,
         .isolate = paintable_box().computed_values().isolation() == CSS::Isolation::Isolate,
-        .is_fixed_position = paintable_box().is_fixed_position(),
         .transform = {
             .origin = transform_origin.scaled(to_device_pixels_scale),
             .matrix = matrix_with_scaled_translation(transform_matrix, to_device_pixels_scale),