dev: Make deprecation warnings more verbose in PHPUnit

This option was needed before because there were a lot of deprecations
that we couldn't resolve unless upgrading to latest versions of Symfony
/ Doctrine. Now that it's solved, we can re-enable the default
behaviour.

.phpunit.xml.dist

@@ -13,7 +13,6 @@
         <ini name="error_reporting" value="-1" />
         <server name="APP_ENV" value="test" force="true" />
         <server name="SHELL_VERBOSITY" value="-1" />
-        <env name="SYMFONY_DEPRECATIONS_HELPER" value="weak" />
     </php>
 
     <testsuites>