Removed one undefined HTML entity in the content of one Czech translation

As reported in https://github.com/symfony/symfony-marketing/issues/167, switching to the Czech locale resulted in `500 Internal Server Error` on symfony.com.

The cause of this problem was the use of the `&hellip;` HTML entity in one translation:

```
An exception has been thrown during the rendering of a template
("[ERROR 94] Validation failed: no DTD found ! (in n/a - line 2, column 21)
[ERROR 26] Entity 'hellip' not defined (in n/a - line 260, column 86)") in
[...]/menu.html.twig at line 14.
```