LibWeb: Don't override main size during flex item cross sizing

There's no need to override the sizes before calculating the cross size.

Besides, by the time we're calculating the hypothetical cross size of
flex items, we may already have established a definite main size anyway,
so overriding it would be wrong.

Userland/Libraries/LibWeb/Layout/FlexFormattingContext.cpp

@@ -1021,11 +1021,6 @@ void FlexFormattingContext::determine_hypothetical_cross_size_of_item(FlexItem&
         // NOTE: Flex items should always create an independent formatting context!
         VERIFY(independent_formatting_context);
 
-        if (is_row_layout()) {
-            box_state.set_content_width(resolved_definite_main_size(item.box));
-        } else {
-            box_state.set_content_height(resolved_definite_main_size(item.box));
-        }
         independent_formatting_context->run(item.box, LayoutMode::Normal);
 
         if (is_row_layout())