remove Security deps from the require section

These requirements have been moved in #20075 before and are still
present in the `require-dev` section.

Author: xabbuh

composer.json

@@ -29,8 +29,6 @@
         "symfony/filesystem": "~2.8|~3.0",
         "symfony/finder": "~2.8|~3.0",
         "symfony/routing": "~3.1.10|^3.2.3",
-        "symfony/security-core": "~2.8|~3.0",
-        "symfony/security-csrf": "~2.8|~3.0",
         "symfony/stopwatch": "~2.8|~3.0",
         "doctrine/cache": "~1.0"
     },