Ensure not to use singleton for form

When using Injector to create a singleton constructor arguments are
ignored. This causes getForm to fail as SAMLLoginForm requires
constructor arguments.

src/Control/SAMLController.php

@@ -348,6 +348,6 @@ public function getLogger()
      */
     public function getForm()
     {
-        return Injector::inst()->get(SAMLLoginForm::class, true, [$this, SAMLAuthenticator::class, 'LoginForm']);
+        return Injector::inst()->get(SAMLLoginForm::class, false, [$this, SAMLAuthenticator::class, 'LoginForm']);
     }
 }