IMPROVE: remove user_external example from config.sample.php

Signed-off-by: Jonas Sulzer <jonas@violoncello.ch>

config/config.sample.php

@@ -277,18 +277,6 @@ $CONFIG = array(
  */
 'skeletondirectory' => '/path/to/nextcloud/core/skeleton',
 
-/**
- * The ``user_backends`` app (which needs to be enabled first) allows you to
- * configure alternate authentication backends. Supported backends are:
- * IMAP (OC_User_IMAP), SMB (OC_User_SMB), and FTP (OC_User_FTP).
- */
-'user_backends' => array(
-	array(
-		'class' => 'OC_User_IMAP',
-		'arguments' => array('{imap.gmail.com:993/imap/ssl}INBOX')
-	)
-),
-
 /**
  * If your user backend does not allow password resets (e.g. when it's a
  * read-only user backend like LDAP), you can specify a custom link, where the