fix(FN-1969): remove redundant mobile margin on milestone ideas button

- Remove the mobile-specific margin override from .roadmap-suggestion-expand-btn in dashboard styles.
- Rely on existing container spacing so the generate milestone ideas action aligns consistently on small screens.

packages/dashboard/app/styles.css

@@ -34903,10 +34903,6 @@ html .column.drag-over * {
     margin: var(--space-md);
   }
 
-  .roadmap-suggestion-expand-btn {
-    margin: var(--space-md);
-  }
-
   .roadmap-suggestion-actions {
     flex-wrap: wrap;
   }