[Form] Fix #11694 - Enforce RepeatedType options value type check

[Form] Fix #11694 - Enforce RepeatedType options value type check

```
| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | 11694
| License       | MIT
| Doc PR        | none
```

`Symfony\Component\Form\Extension\Core\Type\RepeatedType` allowed passing strings as options, which caused problems as in #11694.