Remove warning (#531)

Remove warning on the page "Individual database query". This warning
comes right in the middle of explaing the order and Extbase execute()
and uses Doctrine DBAL persistence without really explaining why.

This made the already lengthy page confusing without really making
it clear why this warning exists.

If there is the need to use QueryBuilder database persistence
functionality it is probably best to introduce this and handle it
on a separate page.

Resolves: #240

Co-authored-by: Sybille Peters <sybille.peters@uni-oldenburg.de>

Documentation/6-Persistence/3-implement-individual-database-queries.rst

@@ -395,32 +395,6 @@ is translated by Extbase to the following query:
     SELECT * FROM tx_sjroffers_domain_model_offer WHERE title LIKE '%climbing%' AND
         organization IN ('33','47')
 
-.. warning::
-
-   You should always avoid making queries to the persistence layer outside of the domain model.
-   Encapsulate these queries always in a repository.
-
-   Inside of the repositories, you can access the database using a database connection:
-
-   .. code-block:: php
-      :caption: EXT:my_extension/Classes/Domain/Repository/MyRepository.php
-
-       use TYPO3\CMS\Core\Database\ConnectionPool;
-       use TYPO3\CMS\Core\Utility\GeneralUtility;
-
-       $connection = GeneralUtility::makeInstance(ConnectionPool::class)
-           ->getConnectionForTable('tx_sjroffers_domain_model_offer');
-
-       $queryBuilder = $connection->createQueryBuilder();
-       $query = $queryBuilder
-           ->select('*')
-           ->from('tx_sjroffers_domain_model_offer')
-           ->where(...)
-
-       $rows = $query->executeQuery()->fetchAllAssociative();
-
-   You have to handle the creation and maintenance of the objects by yourself.
-
 The method ``execute()`` per default returns a ready-built object and the related objects
 - the complete *Aggregate*. In some cases, though, it is convenient to preserve the "raw data" of the objects,
 e.g., if you want to manipulate them before building objects out of them. For this, you have to execute the