fix: move title from h3 to h2

Co-authored-by: Kévin Dunglas <[email protected]>

Author: vinceAmstoutz

core/doctrine-filters.md

@@ -12,7 +12,7 @@ A Doctrine MongoDB ODM filter is basically a class implementing the `ApiPlatform
 API Platform includes a convenient abstract class implementing this interface and providing utility methods: `ApiPlatform\Doctrine\Odm\Filter\AbstractFilter`.
 
 
-### Using Doctrine ORM Filters
+## Using Doctrine ORM Filters
 
 Doctrine ORM features [a filter system](https://www.doctrine-project.org/projects/doctrine-orm/en/latest/reference/filters.html) that allows the developer to add SQL to the conditional clauses of queries, regardless of the place where the SQL is generated (e.g. from a DQL query, or by loading associated entities).
 These are applied to collections and items and therefore are incredibly useful.