Fix long line introduced in commit bb01ea73 ("qapi/block:
Restrict vhost-user-blk to CONFIG_VHOST_USER_BLK_SERVER").

Suggested-by: Markus Armbruster <armbru@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20220119121439.214821-1-f4bug@amsat.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>