Move "Log in with" label to "sociallogin" app

https://github.com/nextcloud/server/pull/16832#issuecomment-528197965

Signed-off-by: Jochen <rothjochen@gmail.com>

core/templates/login.php

@@ -9,7 +9,6 @@ script('core', 'dist/login');
     <div id="alternative-logins">
         <?php foreach($_['alt_login'] as $login): ?>
             <a class="button primary <?php p($login['style']); ?>" href="<?php print_unescaped($login['href']); ?>" >
-                <?php p($l->t('Log in with')) ?>
                 <?php p($login['name']); ?>
             </a>
         <?php endforeach; ?>