Fix translator cache_dir default value reference

According to https://github.com/symfony/symfony/blob/5.4/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Configuration.php#L831 is the default value without a `/` at the end.

Author: smoench

reference/configuration/framework.rst

@@ -2508,7 +2508,7 @@ translator
 cache_dir
 .........
 
-**type**: ``string`` | ``null`` **default**: ``%kernel.cache_dir%/translations/``
+**type**: ``string`` | ``null`` **default**: ``%kernel.cache_dir%/translations``
 
 Defines the directory where the translation cache is stored. Use ``null`` to
 disable this cache.