gpui: Pass Style by value to request_layout (#11597)

A minor thing I've spotted and decided to fix on the spot.
It was being cloned twice within the body of that function (one of which
was redundant even without this PR); now in most cases we go down from 2
clones to 0.
Release Notes:

- N/A

crates/workspace/src/pane_group.rs

@@ -810,7 +810,7 @@ mod element {
             style.flex_basis = relative(0.).into();
             style.size.width = relative(1.).into();
             style.size.height = relative(1.).into();
-            (cx.request_layout(&style, None), ())
+            (cx.request_layout(style, None), ())
         }
 
         fn prepaint(