fix(usage): let the first breakdown row lose its top border

The rule was there to drop the line above the first row, but List
returned a fragment, so the rows were siblings of the section header and
the first one was never :first-child. Wrapping them makes the rule apply
rather than deleting a line that was describing the intent correctly.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: talissoncosta

frontend/web/components/pages/usage/components/UsageBreakdown/components/List/List.tsx

@@ -25,7 +25,7 @@ const List: FC<ListProps> = ({ rows }) => {
   const shares = sharesOf(rows.map((row) => row.value))
 
   return (
-    <>
+    <div>
       {rows.map((row, index) => (
         <Row
           key={row.key}
@@ -36,7 +36,7 @@ const List: FC<ListProps> = ({ rows }) => {
           share={shares[index]}
         />
       ))}
-    </>
+    </div>
   )
 }