docs(www): fix typo in site-header.tsx (#6897)

Fixed a small typo in the site-header.tsx

Author: kasperaamodt

apps/www/registry/new-york/blocks/sidebar-16/components/site-header.tsx

@@ -19,7 +19,7 @@ export function SiteHeader() {
   const { toggleSidebar } = useSidebar()
 
   return (
-    <header className="fle sticky top-0 z-50 w-full items-center border-b bg-background">
+    <header className="flex sticky top-0 z-50 w-full items-center border-b bg-background">
       <div className="flex h-[--header-height] w-full items-center gap-2 px-4">
         <Button
           className="h-8 w-8"