Update page_creation.rst remove unstyled diff symbol

This is a left over from docs showing both annotation and attribute route methods.  The plus sign isn't handled because the code block is not a diff.  Issue was brought up by a confused user.

Author: gizmola

page_creation.rst

@@ -104,7 +104,7 @@ You can now add your route directly *above* the controller:
         // src/Controller/LuckyController.php
 
         // ...
-        + use Symfony\Component\Routing\Annotation\Route;
+        use Symfony\Component\Routing\Annotation\Route;
 
         class LuckyController
         {