bug: ajv example validation

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### Describe the bug

Steps to reproduce

```bash
git clone https://github.com/mosoriob/loopback-next.git
cd loopback-next/
cd sandbox/validation-ajv
npm install
npm test
```

## Current Behavior

The test fail with error:

```
Request POST /pets failed with status code 500. Error: strict mode: unknown keyword: "example"
```

## Link to reproduction sandbox

https://github.com/mosoriob/loopback-next.git

## More details

The API was generated using `lb4 openapi`

```
$ lb4 openapi pet.yaml
Loading pet.yaml...
? Select controllers and/or service proxies to be generated: OpenApiController
create src/models/pet.model.ts
create src/models/new-pet.model.ts
create src/models/error.model.ts
create src/controllers/open-api.controller.ts
npm WARN deprecated querystring@0.2.0: The querystring API is considered Legacy. new code should use the URLSearchParams API instead.

added 38 packages, and audited 609 packages in 10s

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run `npm fund` for details

found 0 vulnerabilities
```

### Logs

_No response_

### Additional information

Similar to: https://github.com/loopbackio/loopback-next/issues/4939

### Reproduction

https://github.com/mosoriob/loopback-next.git

Start in the sandbox/validation-ajv reproduction and run npm install followed by npm test to confirm the strict-mode error for the example keyword. Trace the API generated by lb4 openapi and identify why validation rejects that keyword; done means the reproduction test no longer fails with the unknown-keyword error.

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