layout: Remove clearance parameter from BoxFragment::new() (#37921)

Clearance only applies to block-level boxes, so it was unnecessary to
require it as a parameter. Instead, in block layout we can set it using
the new `.with_clearance()` method.

Testing: Unnecessary (no behavior change)

Signed-off-by: Oriol Brufau <obrufau@igalia.com>

components/layout/flexbox/layout.rs

@@ -298,7 +298,6 @@ impl FlexLineItem<'_> {
             flex_context
                 .sides_to_flow_relative(item_margin)
                 .to_physical(container_writing_mode),
-            None, /* clearance */
             self.layout_result.specific_layout_info,
         );