remove invalid version of symfony/security-http
remove invalid version of symfony/security-http

The split of the Symfony Security component was done with the release of
Symfony 2.4.

kdambekalns/security-advisories,Ocramius/security-advisories,FriendsOfSilverStripe/security-advisories,FriendsOfPHP/security-advisories,marcomenzel/security-advisories,markstory/security-advisories