Form builder shows Join tables

### Before opening, please confirm:

- [X] I have [searched for duplicate or closed issues](https://github.com/aws-amplify/amplify-adminui/issues?q=is%3Aissue+).
- [X] I have read the guide for [submitting bug reports](https://github.com/aws-amplify/amplify-adminui/blob/main/CONTRIBUTING.md#bug-reports).
- [X] I have done my best to include a minimal, self-contained set of instructions for consistently reproducing the issue.
- [X] I have removed any sensitive information from my code snippets and submission.

### App Id

d1d64siqsqavbr

### Region

us-east-1

### Environment name

dev

### Figma File Version (if applicable)

_No response_

### Amplify CLI Version

_No response_

### If applicable, what version of Node.js are you using?

_No response_

### What operating system are you using?

_No response_

### Browser type?

_No response_

### Describe the bug

Creating a new form shows join table in the list

### Expected behavior

join table should not be visible

### Reproduction steps

1. create data models for example:

```
type Permissions @model @auth(rules: [{allow: public}]) {
id: ID!
name: String!
description: String
created_at: AWSDateTime
updated_at: AWSDateTime
created_by: ID
Rolesatye: [Roles!] @manyToMany(relationName: "PermissionsRoles")
}

type Roles @model @auth(rules: [{allow: public}]) {
id: ID!
name: String
description: String
created_at: AWSDateTime
updated_at: AWSDateTime
created_by: ID
permissionss: [Permissions] @manyToMany(relationName: "PermissionsRoles")
}
```
2. open ui builder enable form builder and relationships
3.use the drop down in the new form and observe the join table

### Project Identifier

_No response_

### Additional information

_No response_

Start in the UI builder's form builder relationship flow and reproduce the issue with the provided Permissions and Roles schema. Trace how the new-form model dropdown is populated; done when the generated many-to-many join table is absent from the list while the user-facing models remain available.

Written by the indexing model from the issue text.