issues: fix num items button (#92365)

Use transparent variant button so that this looks like before in ui2


https://github.com/user-attachments/assets/c707a822-0f05-460b-a0ef-dd4a1cd6db0c

Fixes DE-15

Author: JonasBa

static/app/components/structuredEventData/collapsibleValue.tsx

@@ -63,6 +63,7 @@ export function CollapsibleValue({
       {shouldShowToggleButton && !isExpanded ? (
         <NumItemsButton
           size="zero"
+          priority="transparent"
           onClick={() => {
             expand();
             setIsExpanded(true);