Locked dbal to 2.9.2

Locked dbal to 2.9.2

Because the 2.9.3 seems to break test.
Like a conflict with `DoctrineTestBundle` I guess (which can't be updated because we are still allowing PHP 7.1 and is not).

The generated error usually appear when we update data using a service during test (like changing the craue config).
Here is the error:

```
Testing tests/Wallabag/CoreBundle/Controller/
PHP Fatal error:  Uncaught PDOException: There is no active transaction in /Users/jeremy/Sites/github/wallabag/vendor/dama/doctrine-test-bundle/src/DAMA/DoctrineTestBundle/Doctrine/DBAL/StaticDriver.php:142
Stack trace:
#0 /Users/jeremy/Sites/github/wallabag/vendor/dama/doctrine-test-bundle/src/DAMA/DoctrineTestBundle/Doctrine/DBAL/StaticDriver.php(142): PDO->rollBack()
#1 /Users/jeremy/Sites/github/wallabag/vendor/dama/doctrine-test-bundle/src/DAMA/DoctrineTestBundle/PHPUnit/PHPUnitListener.php(39): DAMA\DoctrineTestBundle\Doctrine\DBAL\StaticDriver::rollBack()
#2 /Users/jeremy/Sites/github/wallabag/vendor/bin/.phpunit/phpunit-7.4/src/Framework/TestResult.php(412): DAMA\DoctrineTestBundle\PHPUnit\PHPUnitListener->endTest(Object(Tests\Wallabag\CoreBundle\Controller\ConfigControllerTest), 3.3917479515076)
#3 /Users/jeremy/Sites/github/wallabag/vendor/bin/.phpunit/phpunit-7.4/src/Framework/TestResult.php(893): PHPUnit\Framework\TestResult->endTest(Object(Tests\Wallabag\CoreBundle\Controller\ConfigControllerTest), 3.3917479515076 in /Users/jeremy/Sites/github/wallabag/vendor/symfony/symfony/src/Symfony/Component/HttpKernel/Controller/ControllerResolver.php on line 91

Fatal error: Uncaught PDOException: There is no active transaction in /Users/jeremy/Sites/github/wallabag/vendor/symfony/symfony/src/Symfony/Component/HttpKernel/Controller/ControllerResolver.php on line 91

InvalidArgumentException: The controller for URI "/config" is not callable. The "kernel" service is synthetic, it needs to be set at boot time before it can be used. in /Users/jeremy/Sites/github/wallabag/vendor/symfony/symfony/src/Symfony/Component/HttpKernel/Controller/ControllerResolver.php on line 91

Call Stack:
    3.4732   57305872   1. Symfony\Component\Debug\ErrorHandler->handleException() /Users/jeremy/Sites/github/wallabag/vendor/symfony/symfony/src/Symfony/Component/Debug/ErrorHandler.php:0
    3.5000   58014320   2. Symfony\Component\Debug\ErrorHandler->handleException() /Users/jeremy/Sites/github/wallabag/vendor/symfony/symfony/src/Symfony/Component/Debug/ErrorHandler.php:613
```