bug #8850 change to TranslatorInterface (giansalex)

This PR was merged into the 4.0 branch.

Discussion
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change to TranslatorInterface

Commits
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ff8acaa update to translatorInterface

Author: weaverryan

translation.rst

@@ -120,9 +120,9 @@ for example, that you're translating a simple message from inside a controller::
 
     // ...
     use Symfony\Component\HttpFoundation\Response;
-    use Symfony\Component\Translation\Translator;
+    use Symfony\Component\Translation\TranslatorInterface;
 
-    public function index(Translator $translator)
+    public function index(TranslatorInterface $translator)
     {
         $translated = $translator->trans('Symfony is great');
 
@@ -199,9 +199,9 @@ Message Placeholders
 Sometimes, a message containing a variable needs to be translated::
 
     use Symfony\Component\HttpFoundation\Response;
-    use Symfony\Component\Translation\Translator;
+    use Symfony\Component\Translation\TranslatorInterface;
 
-    public function index(Translator $translator, $name)
+    public function index(TranslatorInterface $translator, $name)
     {
         $translated = $translator->trans('Hello '.$name);