[composer] change ext/intl to the new ext-intl syntax

src/Symfony/Component/Locale/composer.json

@@ -20,6 +20,6 @@
         "php": ">=5.3.2"
     },
     "suggest": {
-        "ext/intl": ">=5.3.2"
+        "ext-intl": ">=5.3.2"
     }
 }