fix(web): remove stray onSubmit on delete form

Server components can't pass function props (onSubmit handlers etc.) to
client-rendered HTML elements. The handler here was a no-op leftover —
removing it fixes the 500 'Event handlers cannot be passed to Client
Component props' on /memories/[id].

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/app/(authed)/memories/[id]/page.tsx

@@ -126,11 +126,7 @@ export default async function MemoryDetailPage({
       </Card>
 
       {!isEditing ? (
-        <form
-          action={deleteMemoryAction}
-          onSubmit={() => undefined}
-          className="flex justify-end"
-        >
+        <form action={deleteMemoryAction} className="flex justify-end">
           <input type="hidden" name="id" value={m.id} />
           <Button type="submit" variant="danger" size="sm">
             Delete memory