Remove outdated index view pitfall from app agent docs (#23667)

## Context

Index views are now auto-generated by a metadata side effect when an
object is created, so the "Common Pitfalls" entry warning against
creating an object without an associated index view is obsolete.

## What changed

Removed the line "Creating an object without an index view associated.
Unless this is a technical object, user will need to visualize it."
from:

- the `create-twenty-app` template
(`packages/create-twenty-app/src/constants/template/AGENTS.md`), used
for newly scaffolded apps
- the 14 existing copies across `packages/twenty-apps` (`AGENT.md` /
`AGENTS.md` / `CLAUDE.md` / `LLMS.md` in `examples`, `public`, and
`internal` apps)

The other pitfalls (navigationMenuItem, front-component scroll) are
unchanged since they still apply.

---
_Generated by [Claude
Code](https://claude.ai/code/session_01YYzo4dY3V7QXdDZtvk5FwY)_

<!-- This is an auto-generated description by cubic. -->
<a
href="https://cubic.dev/pr/twentyhq/twenty/pull/23667?utm_source=github"
target="_blank" rel="noopener noreferrer"
data-no-image-dialog="true"><picture><source
media="(prefers-color-scheme: dark)"
srcset="https://www.cubic.dev/buttons/review-in-cubic-dark.svg"><source
media="(prefers-color-scheme: light)"
srcset="https://www.cubic.dev/buttons/review-in-cubic-light.svg"><img
alt="Review in cubic"
src="https://www.cubic.dev/buttons/review-in-cubic-dark.svg"></picture></a>
<!-- End of auto-generated description by cubic. -->

packages/twenty-docs/developers/extend/apps/data/objects.mdx

@@ -139,4 +139,4 @@ Changes to `isNullable` are applied on every sync, including syncs that update a
 
 - **Connect this object to others** — see [Relations](/developers/extend/apps/data/relations) for the bidirectional relation pattern.
 - **Add fields to objects from other apps** — see [Extending Objects](/developers/extend/apps/data/extending-objects) for `defineField()`.
-- **Display this object in the UI** — see [Views](/developers/extend/apps/layout/views) and [Navigation Menu Items](/developers/extend/apps/layout/navigation-menu-items) to put it in the sidebar.
+- **Display this object in the UI** — see [Navigation Menu Items](/developers/extend/apps/layout/navigation-menu-items) to add a sidebar entry; see [Views](/developers/extend/apps/layout/views) to add custom list configurations.