Fix small typo (#459)

Author: mercuryseries

README.md

@@ -286,7 +286,7 @@ use Symfony\Component\Security\Http\Authenticator\Passport\Passport;
 use Symfony\Component\Security\Http\Authenticator\Passport\SelfValidatingPassport;
 use Symfony\Component\Security\Http\EntryPoint\AuthenticationEntryPointInterface;
 
-class MyFacebookAuthenticator extends OAuth2Authenticator implements AuthenticationEntrypointInterface
+class MyFacebookAuthenticator extends OAuth2Authenticator implements AuthenticationEntryPointInterface
 {
     private $clientRegistry;
     private $entityManager;