Update SYMFONY_PHPUNIT_VERSION to 9.6 (#1258)

Author: louismariegaborit

symfony/phpunit-bridge/6.3/phpunit.xml.dist

@@ -14,7 +14,7 @@
         <server name="APP_ENV" value="test" force="true" />
         <server name="SHELL_VERBOSITY" value="-1" />
         <server name="SYMFONY_PHPUNIT_REMOVE" value="" />
-        <server name="SYMFONY_PHPUNIT_VERSION" value="9.5" />
+        <server name="SYMFONY_PHPUNIT_VERSION" value="9.6" />
     </php>
 
     <testsuites>