Clippy fixes from rust 1.91 nightly (#1267)

src/utils.rs

@@ -179,7 +179,7 @@ pub mod merge_strategies {
         if let Some(left_vec) = left {
             if let Some(mut right_vec) = right {
                 right_vec.append(left_vec);
-                let _ = std::mem::replace(left, Some(right_vec));
+                let _ = left.replace(right_vec);
             }
         } else {
             *left = right;