Fixes an issue with comparison operators like <,>

the contao core strips some comparison operators in a custom sql query like

```sql
select id from mm_table where tstamp >= 1 and tstamp < 100;
```
to
```sql
select id from mm_table where tstamp
```
when you save the form.

with `preserveTags => true` and `decodeEntities => true` the query gets saved properly.