Fix EZP-23622: Link for "For more options try the advanced search" in DemoBundle loses words

### EZP-23622: Link for "For more options try the advanced search" in DemoBundle loses words

If you make a search of two words (New Article) in the Search input box in Demobundle, when it displays the results it will also show a link for "For more options try the advanced search". This link will only consider the first word, ignoring the other ones
Nitpick: why not modify the var `set` instead (looks cleaner, IMHO)?

```
{% if searchText %}
    {% set advancedSearchUrl = '?SearchText=' ~ searchText|replace({' ': '+'} %}
{% endif %}
```
Other than that +1