docs(config.sample.php):

When setting a custom `updatedirectory` it's important that it not be located within the Server installation folder structure.

Partially addresses nextcloud/updater#463

Signed-off-by: Josh <josh.t.richards@gmail.com>

config/config.sample.php

@@ -1870,7 +1870,9 @@ $CONFIG = [
  * where the default `datadirectory` is on network disk like NFS, or is otherwise
  * restricted. Defaults to the value of `datadirectory` if unset.
  *
- * The Web server user must have write access to this directory.
+ * If set, the value MUST be located _outside_ of the installation directory of Nextcloud and
+ * writable by the Web server user.
+ *
  */
 'updatedirectory' => '',