[Validator] Updated outdated dependencies.

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Fixes tests for the ```Validator``` component when using it as a standalone library (when running ```phpunit``` from the ```src/Symfony/Component/Form``` directory.